2008 LS getting a little warm?

Per my previous threads, I recently did A LOT of work to it. But in case you didn't feel like visiting those threads:

1) replaced heater core
2) replaced head gasket
3) replaced water pump
4) replaced timing chain during the head gasket change
5) even replaced the coolant reservoir cap
6) replaced green coolant with DexCool (red).
7) replaced the injectors, o-rings, and injector sleeves

Note: I have a bad catalytic converter right now as well. It's been like that since I got it.

This was during the beginning of summer when I did all of this work. After all was finished, it was running great (except for the cat). The temperature never reached higher than 200F. It usually stayed around 194-196. It was a dream come true.

Now, literally out of nowhere (no progression to this state. Just one day BAM), it's getting far warmer than usual. While I'm driving it never goes below 205F, and at stoplights it worries me, because it goes into the 220s, and I've even seen it get to 230-235F.

WHAT IS HAPPENING?! I have a 20 mile drive to work everyday, and I simply can't afford to dump anymore money into this headache. I was limited on options when purchasing a car, and went with the first seller that contacted me (big mistake).

It ran great for a solid month. I could idle all day long and it never got warmer than normal.

Oh boy... I hate to offer up ideas that could cost you more money, but here goes...
First things first: I am NOT a professional mechanic, and I'm not a die hard that can point to one exact issue. That said, I'm not completely useless under the hood.

I can see a few possibilities here. Did you back flush or power flush the cooling system when you changed coolant types, and are you positive you got a 100% coolant change? If no, it's possible that there could be sludge in the radiator. Dex and green coolant hate each other, and can sludge up if mixed. If your coolant change is not at fault, it's possible that there may have been other debris or sludge on the radiator causing a blockage. One way to possibly check this is to crank up the heat inside the car (Which really sucks in the summer) and watch your temp, if it goes down, it may be a radiator issue. Or you can remove a coolant hose and try to visually inspect the small section of radiator you can see.
Another option: your electric fans. Simply put, make sure they're running when they should be. Simply test by idling your warm engine and popping the hood.
Not likely, but possible nonetheless: your thermostat could be faulty. I know you replaced it recently, but there's a chance it might be defective. You can test it by pulling it out when it's cold, and putting it in hot water (if you can monitor the water temp, try to have it around the temp you're used to seeing). If the thermostat opens up it's fine, if not, see if you can get it exchanged.

Or you could just go ROADKILL with it and remove your hood... Just saying... It works...

Another thought... Perhaps stop at your local lube shop (I think AutoZone does this too) and ask them to pressure test your cap. A bad cap can cause problems, but I'm not sure if overheating is one of them, someone correct me if I'm wrong there.

I suspect, as Kobra mentioned, that your electric fans aren't turning on. If you start the car and turn on the A/C, do both radiator fans come on?

Temperatures for these cars are usually around 210 in the hotter months so seeing 220 isn't a huge worry, 230-235 has me slightly concerned but it's still within an acceptable range in my opinion.

I tested the thermostat in water when I did the water pump and it opened as it should have.
The fan (I only have one) kicks on around 220°. Whether it's in high mode, I don't know.

I had the catalytic converter replaced. It drives SO much better, but it still gets warm, mainly when idling or going up hill.

No I'm not positive all the green coolant was gone from the radiator, so I can't tell you for sure.

I'm just so confused because it didn't even get above 200° a month ago. It could idle forever and stay the same. I could go up hills with no change.
Now all pf a sudden it just jumps up quickly, then as soon as the hill plateaus it starts going back down, but it stays around 208° at the very least.

Even when summer really kicked in down here in the South it stayed normal.

The ONLY thing I have no replaced is the radiator, but it's so strange how it was fine for that length of time.

From my previous threads on this issue, I have done the following:

Head gasket
Water pump
Thermostat
Heater core
Cap
Timing chain
Injectors/sleeves

It runs great. No more idle problem, no more sluggish acceleration (the mechanic showed me my converter. It was clogged). It just gets hot when the engine is under load or I'm at a stoplight.

Looks like I'm gonna have to hock some of my music equipment to get this done because I'm out of funds. Lol.

One thing I did remember was that when I did all that work, I kept having to remove and replace the coolant. I ran short because of a spill, so I just put whatever I could back into the system. When it's sitting cold after not running for a while, the level in my reservoir is all the way at the bottom. Would this make a significant difference? I didn't think it would, so I ignored it until I remembered to stop and grab some coolant.

I also checked my oil when I went outside and it still looks good, so my head gasket job was a success thus far.

So long as there is still some coolant in the tank when hot it should be ok. If not then you're going to push air bubbles into the system. It self burps for the most part though so you should be ok.

Mine has been running hot this week as well, it has been rather warm outside. So long as the temperatures come back down once moving again or after the hill I'd say you're fine. You can check that the coolant is mixed correctly for your location if that helps. I swear, GM should have just put a little needle instead of numbers. Would save a lot of guessing since they don't tell us what normal operating temperature is for the motor.

The cooling problem is done. It was low. See my newest thread for my latest and most serious issue.