Ok so I'm bad at computer stuff and....

[lyndwyrm]

Closing skype/Using only one mic chat program during the game.

As others have said, a score at 8300 is plenty high. High enough that not many programs you would leave open in the background would slow you down.

Defragmenting - I think my comp says 2% fragmented, and I'm wondering if this has much to do with my score

Defragmenting would only really affect load times, and is only relevant if you're running off of a HDD. IIRC, Windows 7-10 schedules defrags automatically, so this probably isn't even a problem then. If you're running an SSD there's no benefit to defragmenting and Windows 7-10 would have this default to off.

Clearing cookies

Cookies are just browser data, so this really shouldn't have an effect.

Cleaning the dust out of my comp tower - Probably should do this, since I don't think I have in the 4-ish years I've had this (Got it 2 months before A Realm Reborn)

Possibly keeping the temp in my room a bit colder - Since I know comps can get hot, even with good cooling systems, and I'm wondering if the temp being lower in my room helps.

Cleaning dust out would be a good idea, just use a can of compressed air and focus on tight areas of heat sinks. This will probably be on top of the CPU and likely also the Graphics card. If you're not confident doing that, try and find someone that is confident and will show you. It is simple, but having a demonstration never hurt.

Cooling your room however, will probably just be a waste of money for the A/C.

Also I don't know how to check the specs of my comp to actually say what I'm using, so help on that would be greatly appreciated. All I can say it that it's an alienware gaming comp I got as a birthday gift.

When you're running the benchmark, your main specs are the 4 lines of text beneath the "Visit the Official Website" button. Like:

Windows 10 Pro 64-bit (6.2, Build 9200) (14393.rs1_release_sec.170327-1835)
Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
NVIDIA GeForce GTX 980 Ti (VRAM 6103 MB) 
1920x1080 Maximum Borderless Windowed

The middle two lines are your CPU and Graphics card.