It's important to be clear about terms. Hypotheses are just guesses. Through experimentation and observation, they can become theories, which are just well-tested hypotheses. Theories can explain why something happens. It's not accurate to state that a "theory is true;" it's accurate to say that it is "accurate." In addition, through countless experiments and observations, facts, or that which is true, can be determined. Something that summarizes the facts can be described as a law. It is accurate to state that a law is true.
It's critical to understand that theories are not laws, that theories are not facts. Theories and Laws are apples and oranges. Theories explain why something happens, Laws dictate what will happen. Neither ever transforms into the other.
Inductive reasoning was the key to the Scientific Revolution. Hypotheses could be stated. By observation, and experimentation, theories could be produced and facts can be determined; eventually a body of related facts could be comprehended as a Law, or a summary of many facts. The classic case of this process was Galileo's obeservations and hypotheses regarding motion, that a generation later, were codifed by Newton into his mathematical formulas describing the Laws of Motion and Gravity.
Contrasted with inductive reasoning is deductive reasoning, where axioms (truths) are stated, and from which other truths are derived. Before the Scientific Revolution, in the Western world, this process held sway for two millennia, from the time Aristotle stated "facts" from which other facts were derived. Authorities may dictate facts, but without the rigor of observation and experimentation, they may in reality be only hypotheses, or opinions from someone in authority.
The issue between the "hard" and "soft" sciences is that "natural" sciences are inductive and the "human" sciences are deductive. One can be convinced by the natural sciences because of the rigor they present; one is not so convinced by the human sciences because the rigor is absent. Axioms from authorities are not equal to Laws composed of facts.
I agree that theories have something more than mere hypotheses. Theories have evidence and facts to support the idea. They can be readily observed and often have scientific data behind them. While a theory has not or cannot be proved, it is still very convincing because it does have some form of proof behind it. The way we interpret the evidence behind a particular theory may determine our level of belief in that theory. In general, theories are believable because they have quantifiable evidence supporting them.
One thought: the objects of theories in the "hard" sciences do not, for the most part, have free will. Their behavior is therefore very exactly predictable. Thus it is easier to propose testable, objective theories in the hard sciences. This is much less easy to to in the social sciences because people do have free will. They can often change their minds and behavior if they choose to do so. Therefore, formulating valid theories in the social sciences is much more difficult.
Theories are convincing because they conform to observation. They are formed inductively, in other words, from quantifiable data and observations. If observations don't jibe with the predictions made by a theory, then (after ensuring that the data are right) scientists must alter their theory. It's important to note that the way we use the word "theory" in popular speech is not the same thing that it means to scientists. Logically, theories can't be proven correct, which often exposes them to popular criticism. They can, however, be falsified or profoundly altered by observations and data that do not match their predictions. The great scientific theories (evolution by natural selection, to cite one example) have withstood enormous scrutiny, and the predictions that scientists generate using them have generally matched the data collected.
As for the difference between social sciences and other sciences, I think it's important to remember that history and other humanities are not really under the rubric of social science. There are certainly intersections in a number of different fields (anthropology, psychology, and political science, in particular.) The social sciences, however, are more similar to other sciences in terms of the mechanics of developing and testing hypotheses and theories.
These are very different things. In the natural sciences, theories are convincing because they have physical proof. Scientists can show that the world has warmed up, so we can be convinced that global warming is occuring. Within the social sciences, it is much different. Theories there can only be convincing if they make logical sense to us. Whether they do or not is based largely on our own beliefs and prejudices.