Camaro RS '15 various issues

[Pendra37]

Hi guys!

I recently bought a Camaro RS 2015 with 85k miles in the clock for a reasonable price. I'm the 3rd owner. Let's just say the 2nd owner did not look after the car much. He changed the oil+filters and the pads that is about it in 4 years. It is driving but is not in a great shape.
I plan to use it as a weekend car for some years and then give it to my son to impress the chicks .

I'm still compiling all the stuff I need to take care of or have checked out. Every input, feedback or generic advice would be welcome!

- The electric brake booster vacuum hose is cracked. Yet the brakes work fine. I wonder what is the point of that thing? Should I get a replacement hose or just have the pump and the hose deleted?

- Half the black cable hoses crumble to dust just by looking at them. I ordered some replacement hoses which are rated until 250F. Would that be OK under the hood, next to the engine? *

- The cooling feels weird. The temp gauge below the speedometer barely moves from the 1/4th position. Meanwhile the digital thermometer deviates between 170-220F. Also 220F is a bit high to me. I checked the radiator (full) and the overflow tank (diptick shows empty). I put a quart of coolant to top up and now the dipstick shows max (cold or warm). Odd.
Also I plan to replace the coolant anyway, should I use the Dex-Cool or is there something better, less gunky to use.

- The auto transmission seems to run hot. Mid position on highway but goes near to 3/4th in city driving. I think it is time to change the oil and the filter in it.

- While there, the maintenance schedule shows +5k miles for the brake and diff fluid change. However, I think changing those ahead of schedule would not hurt.

- After running the engine for like min, there is some ticking noise from the back of the engine on the passenger side. You don't hear it in the car, only outside, next to the open the hood. What can that be?

- The thermal insulation material (around the cabin air filter and on the firewall) looks like ****. Any recommendation how to fix that up to look and work half decent?

- There is some fabric on the top back side of the egine. That looks much like the thermal insulator. Filthy, flimsy, broken. What is that fabric for? Can that be thrown out, or fixed up or get some replacement for it.

- The exhaust headers look completely rusted over. What is the best way to remove the rust from there?

- While there, it feels the passenger side exhaust is broken or leaky. Its output is noticeably less than the driver side exhaust. Also, at full throttle, there is a high pitch blowing noise from that side, instead of the regular engine roar. It may also be coming from the transmission thou.