Congrats on turning 21! Here's some handgun 101 info that will help. The caliber of bullet has nothing to do with whether the gun jams or doesn't jam. When it comes to guns for self defense, realize that a 1911 is 100+ year old technology. Yes, they still work fine and they're fun and fantastic to own, but there are better options for self defense. They carry more rounds, aren't as heavy and aren't as finicky.
So let's talk about self defense and break it down into three classes. The home defense gun, the conceal carry gun and in your case, the car gun.
Starting with the car gun, you have to be aware of a couple of things. First is that it's most likely to be stolen because you're not there and cars are broken into all the time. For that reason, a $1000 1911 may not be the best option. Secondly, you must always lock your car or you will likely be in violation of gun safety laws. If you leave your gun in your car and don't lock the car you have unwittingly provided access to a loaded and unlocked gun to minors which is illegal in most states. So my advice for a car gun is to use the one you carry. Just take it out of the holster and stick it in a car holster while you're driving.
For conceal carry, you need a gun you will actually carry. You'll hear a TON of tough guy talk about stopping power but it's ridiculous. If you'll actually carry a little Tauraus PT22 in your pocket all the time, then by all means get a little PT22. As they say... the first rule of a gun fight is to always bring a gun.
Now regarding the "stopping power" myth, I wish the Internet would just STOP with that already. Ask any hunter whether they would rather have a good shot with a 22-250 on a deer or a bad shot with a 300 Win Mag and they'll tell you that they'll take the good shot with the 22-250. The same applies to self defense guns. Shot placement is king and WAYYYYY more important than any caliber discussion. Pick a gun you'll like to practice with so that you can make good shots.
So now that we know that having a gun with you is important AND shot placement rules, I'll just share with you some recommendations for different classes of guns and why I'd recommend them.
CONCEAL CARRY:
1) Single stack subcompact 9mm: Ruger LC9s (not the LC9), S&W Shield, Kahr PM9, Glock 43, Springfield XD, Walther CCP (6-7+1 rounds of 9mm and easy to carry which means likely to be carried. The ammo is cheap and available so you'll practice and all the guns listed are good shooters.)
2) Small frame revolver: Ruger LCR (or LCRx) or the S&W M&P Bodyguard (revolvers are 100% reliable with no failure to feed issues, no failure to eject issues AND they are amazingly comfortable to carry because they don't have hard straight lines like a sem-auto, they sort of mold right to your body)
3) Small 380 Auto: Ruger LCP or S&W Bodyguard, Walther PPK, Glock 42 (the 380's are great guns for self defense. They're basically a 9mm with just a little less energy. They're a lot smaller so they're easier to carry but they're also a little snappy to shoot so that's a consideration.)
CAR GUN: - use your conceal carry gun.
HOME DEFENSE:
1) Double stack full size 9mm: S&W M&P9, Glock 17, Ruger SR9, Kahr, Springfield, Walther PPQ, CZ75, Beretta, Sig, H&K (there isn't a second option because there really isn't a second option. Once you've actually had to defend yourself in your home, you quickly realize the flaws of virtually all other options. You want something that holds enough ammo to deal with multiple intruders or extended confrontations. You want something that only requires one hand to operate in case you are injured, moving or carrying a kid or something. You want something that you can hold in your teeth while you climb out a window to safety. For all those reasons, the double stack 9mm is the best home defense gun.)
In the end, the best advice is for you to pick out a good conceal carry gun and use that as your self defense gun at home, in the car and where ever you are. As funds allow, add a good home defense gun. If you ever get money to play with you'll probably "retire" your conceal carry gun to the car and get something different for carrying.
Final bit of advice. Do NOT buy a Hi Point or a Kel-Tec. They are junk. Taurus is OK, but the brands listed above are better if you can swing the extra $50.