1996 Pontiac Sunfire engine overheat

Engine Cooling problem
1996 Pontiac Sunfire 4 cyl 125 miles

the main problem I have now is that sometimes the engine gets overheat and starts to choke, but if I manage to get some speed sometimes it cools down. I checked the tank for water (onestly I think it supose to be the tank for the water but i'm not sure, it's a big yellow tank near the right head light) and it's empty, I put in like a galon of water and still wasn't full, but i've checked under the car and it's no leak (maybe it just evaporetes or something I guess). It's also a funny smell coming from the alternator I think (witch also has a funny squizy noise) and I just drove the car for like almost 2000 miles and hadn't got any problem. I've just arrived in miami and I think it's too hot or something because I didn't had this problem before on the road. The ac is not working either, I don't know if the problem is connected with the overheating. The only problem that I had was that when I was low on gas, the car started to choke and lost power, when I accelerate my rpm's went down, but when I fueled it up the problem dissapeared. I actually had to push the car for a half a mile to a gas stop because the clock from the gas showed me that I have gas for another 30 miles at least :( but like I said once I get gas there's no problem. Til I arrived in miami, now it's overheating and also sometimes won't start. So I think I have touched most of my problems with my sunfire, really never though i'd have so many problems (just fixed the breaks for 300$ :( ) yeah, forgot to mention it, I changed the air filter and the oil filter, and the oil as well. The fan from the radiator is working fine. Waiting for ur answers please :) thx a lot