Do you think Jim is really a decent guy?
Could we connect the theme of illusion with Jim as well?
Why did he kissed Laura and waited until the end of the evening to admit he is engaged?
Could we say that Jim chose to participate in the illusion of the gentlemen caller because he liked the attention he was getting from Amanda and the beautiful although shy company of Amanda?
Perhaps we could connect Jim with Mitch from The Streetcar Named Desire because they are both marriage candidates for southern heroins who turn out to be less than perfect gentlemen and not interested in the marriage?
For some reason Jim always reminds me of a sort of "Biff" from Death of a Salesman in the tendency for living in the past and off old glories. However, Jim also comes across, like many of the posts, say, as a bit of a hedonist who loves the flattery and attention to which he has been used to since he was in high school. I mean, people seem to always revert to their high school years to configure their lives as adults. It is also as if we, as individuals, have a tendency to think that who we were in high school would preclude what we would become as adults. Hence, Jim must be having a hard time imagining himself back in high school, and seeing what he is now. Like the previous posts said, he likes the attention and he likes the flattery. He likes Tom because he reminds him of his football past. He hides his engagement to kind of go back in time when he was a heartthrob. After he got his taste of it, he at least learned to get back to reality and leave that home which, in itself, is a walk in the past.
I personally think that Jim is subject to the same kind of illusions and daydreams that every other character is prone to in this excellent drama. Note the way he is ideailstically pursuing public speaking classes but has not really made much of himself since graduation. He has high hopes and dreams, and is arguably making more of a success of himself than Tom, but at the same time it is clear he is not entirely in the real world either.
The point about Jim's responsibility to say something about his engagement is one that indicates that he has a propensity to entertain illusions as well. It would seem that he enjoys being the center of attention, just as he basks in the glory of his old high school days. With Laura he is again "the big man on campus" who can boost his ego by talking with the "wall flower." Of course, at first Jim does not realize his importance as the dinner guest. When he does, however, he is candid as he is not truly cruel and does not wish to hurt Laura any further.
Your idea is an interesting one. Jim, the infamous "Gentleman Caller," is often seen as the only "normal," well adjusted character in this play. A closer look shows that he is not the paragon of all virtues which he is set up to be.
You ask if he's really a nice guy, and I think he is--despite his kiss with Laura. He does see what's going on with the matchmaking and plays along rather good-naturedly. It's true he doesn't say anything about his engagement, but he knows that would have ruined the Wingers' evening. I'm certainly not advocating such acts of infidelity, but I sense he's simply being caught up in the moment.
What is more telling to me is that fact that he, too, is stuck in a warehouse job he hates. This is a guy who was presumably a shining star in high school, who has big plans for others, and has ambition for himself; yet he is not really achieving anything with his own life. It's true he's taking a class in order to pursue a career, but he is certainly not a picture of achievement and ambition. In other words, he talks a great game for others but doesn't particularly follow his own advice. He may be more socially adept, but he doesn't actually have much on the Wingers.
I think Jim should have mentioned he was engaged. He would have probably ruined the evening but it would be less traumatic for Laura in the end. Anyway I think that the main reason why Jim kept his engagement secret is a selfish one: he sensed that Laura likes him and was flattered by it.
Jim seems to be able to understand Laura and her self-esteem problems but I do not see him as genuinely being interested in helping Laura. If he had really tried to help Laura, he could have tried to be friends with her. I do not believe he will even again visit her.
You are right about Jim's job prospects.Tom says at one point that Jim is not much more paid than he is. Another thing that Tom says is that basically the reason why Jim enjoys Tom's company is because he recalls Jim's High school glory days. That suggest that Jim is not so full of self-confidence as he would like to be. ( Perhaps he is not in any position to give advice to Laura)
I agree with your conclusion, the only thing Jim has is that he is more socially adept.