u/Ok-Intern7131

I recently moved and hopped onto my new ISP's wifi and was shocked to find that I was either receiving 50 mbps or less download or the network would not even appear on the list for my PC. My ISP contract is for 1G and it tests at about 1.19G on the app. Here's a list of things I've tried so far:

1. Moved to another location in the room. Gained 1 bar of signal but still 50 mbps or less.
2. Moved modem & router to more generalized location. Same result.
3. Move PC to hallway to get direct LOS to router about 20 ft away, got as high as 90 mbps.
4. Wiped PC and booted up fresh, moved PC back to original desired location and get about 45-50 mbps.

The PC is about 4 years old and uses an Intel(r) dual band wireless-AC 3168. I made sure to take extra care when moving it and it took no hard bumps or strikes in the moving process.

What could possibly be the issue here? Could it be age, a fluke component degradation at an inconvenient time? My phone gets 500 mbps download every time I test it in the exact same location and all my other wireless devices are very stable with no buffering or service interruptions. Not really sure what to do here other than run a cable from the router to the tower.

I am needing to drop a cable from my router in the living room through the attic to my office. I will need about 100 ft just to be safe. My ISP is supplying 1G but I plan to upgrade to 2.5G when they have it in my area in a few years.

What cable brands on Amazon provide a reliable, safe Cat 6/6a for traversing an attic space that can get well above 130 during the summers? A link with some quick spec breakdowns for a newbie would be very much appreciated. It may run between the studs where my outlet is wired if that matters.

I've seen the prices of plenum and riser cables that I could crimp myself, but I don't need 1000 ft and am trying to buy only what's needed to safely get the job done. A lot of off brand stuff on Amazon sketches me out so if you have success stories with some brands offered on Amazon that can be used in hot attic spaces I'd love to see what's actually good for home use. I see Monoprice popping up on some older posts and am curious if that's still correct to use for my case.

Thanks!

Edit: thank you to the person/bot that took advantage of this being my first post on this account by downvoting it, hope that doesn't impact me getting the solution I need.

Edit 2: I really appreciate everyone helping out! Hopefully I can get my PC to do better than 15 mbps soon!!