I would absolutely not want to be the individual named "Ace" in the scenario provided, but the extent of his liability, if any, under the conditions specified is uncertain and would be highly dependent upon the rulings of a court or the deliberations of a jury. Tort Law is notoriously complicated. Unlike a criminal case in which a preponderance of physical and/or circumstantial evidence is the measurement by which a decision or verdict is made, civil cases are more tenuous. They rely on interpretations of laws and on sometimes nebulous connections drawn between the conduct of individual A and the injury to individual B.
Once upon a time, Ace would have borne little or no responsibility for the conduct of social guests who consumed excessive quantities of alcoholic beverages provided by the host (in this case, Ace). He certainly made alcohol available to adults but was not considered responsible for the conduct of other adults who consumed that alcohol. Today, as a result of the large number of alcohol-related deaths, especially drunk-driving-related fatalities, civil laws have changed to allow for lawsuits that charge the provider of the alcohol with responsibility for the conduct of the consumer of the alcohol. So-called "dram shop statutes" have been adopted that hold servers of alcohol, mainly restaurants and bars that serve alcohol, liable for the actions of customers who consume excess quantities of alcohol at these commercial establishments and then proceed to cause bodily harm to others, such as from driving under the influence of alcohol. While these statutes were targeted primarily at commercial establishments, they have been extended to include private individuals who serve alcohol to guests with similar adverse consequences.
In the scenario provided, Ace had established an environment in which the possibility of personal harm was definitely present. By placing a keg of beer on his deck "near the swimming pool," he almost invited disaster in the person of an inebriated guest falling into the pool and drowning. That did not occur, but it was possible given the party atmosphere Ace deliberately created. Additionally, while the fireworks that caused an injury to Frieda were brought by uninvited guests, Ace apparently did nothing to control the activities taking place on his property. And herein lies a big part of the problem. Ace had taken no steps to protect the individuals on his property from harm and did, in fact, facilitate the creation of an environment in which injury to guests was a distinct possibility. He could be liable for the injuries that occurred as a direct consequence of the environment he created.
Chuck is certainly liable for his actions. Being under the influence of alcohol is obviously no excuse for initiating a chain of events that led to the injury of a police officer. While the student's question states that criminal matters should not be addressed, Chuck would be arrested and charged with a crime under the scenario provided. The injured police officer could, additionally, file a civil suit against Chuck, as well as against Ace, on whose property a fire was started due to negligent behavior. Ace may not have read the warning label on the propane tank, but, as an adult, and as someone who owns and operates a gas grill, he would be presumed to be knowledgable regarding the fire hazards associated with using a gas grill, especially when that grill and its attached propane tank are in close proximity to fireworks. That's a notoriously bad combination--propane and fireworks--and Ace would be expected to be fully aware of the risks involved.
Could Ace argue before a judge and/or jury that his guests failed to use "due care" and were responsible for their own actions? Chuck, Paul, Frieda and the rest were all, presumably, adults. As such, they bear some measure of responsibility for their actions. Again, however, Ace hosted a party in which alcohol was freely and openly served to his guests. That entails a considerable measure of responsibility on the part of the host under current laws. The fact that his guests knowingly participated in the activities that took place on his property does not absolve Ace of responsibility for injuries that occurred and that were directly connected to his party. If anyone has a potential case here it is Frieda, who was injured by the propane tank explosion. It would be very difficult for Act, as a defendant in a civil case, to successfully argue that Frieda assumed responsibility for her injuries. She was invited to a party, but the individuals playing with the fireworks were uninvited. She was a victim of negligence on the part of the uninvited guests and could also be considered a victim of Ace's negligence, as Ace failed to control the environment on his property. The party was not inherently dangerous, despite the presence of alcohol, and she had no reason to fear for her safety as an invited guest.
The issue of Paul's injury and the inoperable streetlights is the most legally complicated part of the scenario. Electric Company could be held liable for Paul's injuries. Presumably, Electric Company was directly responsible for installation and maintenance of the streetlights. When it assumed that responsibility, it both acknowledged that the streetlights were important for public safety and that it, the utility company, was responsible for the proper operation of those streetlights. Had the company been unaware of the broken streetlight, it might be able to argue that it bore no responsibility for Paul's injuries. If just one call had been made to the company, however, complaining about the inoperable light, then Electric Company could be held liable. Case law on this precise topic is voluminous and varies from state to state. Below are links to legal discussions and court cases specific to real-life cases involving injuries potentially attributable to improperly functioning streetlights. Case law is all over the map on this issue, and the duration of time that the streetlight was inoperable combined with whether or not complaints had been made with the utility company advising of the inoperable light(s) are all factors that would be considered.
Whether Paul is responsible for his own injury is another matter. Again, insufficient information is provided with respect to the chain of events leading to his injury. Was Paul under the influence of alcohol? Was the driver operating his or her vehicle at an unsafe speed? Should common sense--a tenuous proposition in the world of torts--have been a factor? After all, we teach children not to run into streets without watching for cars. The absence of a functional streetlight did not negate that expectation.
In the end, Ace is in a very precarious position regarding liability for injuries connected to his social gathering. Inviting people to such a gathering and serving alcoholic beverages, especially from a keg, the mere presence of which suggests a certain carelessness with regard to the host's ability to monitor guests for excess consumption, involves responsibility for the safety of the guests. Under virtually any formula, Ace appears negligent.