You can buy from a very large set of guns with $600, especially if you include pre-owned guns. But why "as close to a full size as possible" for a carry gun?2) I want to stat CCing, and would prefer as close to a full size pistol as possible, preferably from metal construction (not a huge polymer fan, yes I know it has its advantages). I would prefer either a 9mm or .45acp, as I would assume that the .22lr probably isn't the best choice for SD, although I am a pretty wicked shot, but lets just be subjective. That pistol would need to be around $600ish but preferably a little less, and it MUST have an external safety.
Of the many different pistols you've shot so far, which ones did you like? Which did you not?
The difficulty in keeping concealed generally increases with the size of the gun. But you're right to be concerned about staying concealed. That, after all, is the agreed upon method of carry.3) I am getting freaked out about CCing. Not about carrying a gun, but making sure its concealed. I have what I would call an athletic build, about 5' 10" - 160ish lbs. I dress well, khakis and a polo or button down but sometimes more casually. I see alot of these bigger guys who wear hawaiian shirts not having a problem concealing, but thats not me. I guess I'm not sure how I would pull if off without having to wear a silly tactical vest or sweatpants/shirt.
Recently, there was a guy, young guy like you, and very new to carry, who posted here about how his "weapon was outed" in front of some pretty much anti-gun people. Basically, the guy was just careless and the "outed" gun caused him some grief with his colleagues, though, luckily, it wasn't legal grief. But the tricky thing was that, even though he obviously and solely caused the initial (and continuing) disruption to his, his family's, and some others' lives, he found it hard to take his fair share of responsibility for having caused the grief. He seemed to be more interested in convincing some pretty much antis that guns and gun carry was good for everyone. And he made some rather general and unsupportable allegations that every permit holder has their gun outed so it was understandable that he had done so. This was pure poppycock, but he was all defensive about it. Hopefully, he learned from the incident.
The bottom line was that he had to expend a lot of energy to fix a problem of his own making. You are to be commended for having a high degree of concern about the effectiveness of your concealing before you get out there. Preparation, monitoring and assessment are the key processes. There really is no rule that every carrier has to out his gun. "Outing" can be, and usually is, avoided.
Best of luck to you.