try factory reset to avoid any software bugs. If still same problem may be some bulge or broken capacitor (usual after some years). see Repairing an LCD Display with failed capacitors or look in google images/youtube for replace failed capacitors. Now open TV and see if you can see any leaks (like dark liquid). In ifixit forums also there are tons of people fixing by soldering. Open TV and add picture to this post.
There is no USFF. It is either SFF or micro. If you have SFF then you can use small graphics cards. Search in electroncs shops or eBay or amazon for "half-height" graphics card’ https://www.dellemc.com/resources/en-us/asset/data-sheets/products/desktops-all-in-ones/optiplex_7070_spec_sheet.pdf See page 5
Some apps like FB/whatsapp will save (manythings) only to internal storage. You cannot change it. Either move photos/vides from whatsapp to your SD card or in the file manager look for a folder called Android (just delete it). Every app keep lots of rubbish inside it. In the worst case copy all your photos/videos to Google or computer. Go to Accounts->Remove account->google account. THEN. Reset the phone. A clean reset is the best. Do not reset before removing google account. lets us know if all is then OK.
ideally you need to unlock and then install old ROM, Better see here (add https://) I would suggest install a lineageos based ROM that gives clean and privacy friendly software. Any help ask in XDA forums: https ://forum.xda-developers.com/galaxy-tab-a/development
dell.com/communitAlienwarey/-General-Read-Only/Alienware-Beep-Codes-Table/td-p/5588971 Preliminary check: "as fixed by an on and off, but now we can only get into BIOS and no further. Did you find any solution?" Can you check if bios recognizes all hardware.? "unplug and remove battery Carefully reset RAM modules Reset BIOS Check bios if all RAM is there?" 1 Possible Motherboard (covers BIOS corruption or ROM error) 2 No RAM detected 3 Possible Motherboard Chipset 4 RAM failure (other) 5 CMOS Battery 6 Video card/chip 7 CPU 8 LCD
(1) How old is the device or battery (2) Without any load it may show 3.7V but with load it may fail. (3) Connect battery to tablet - close device - start it - does it work for at least few minutes (4) Do (3) then, connect to charger and the press powerbutton. (5) Can you see the manufactured date in the battery? If it is more thant 3 years - may be better to get a new battery. Search eBay or aliexpress. (Do not connect to charger without battery - some devices can brick)
Replacement HDD larger than 2 TB? May be this helps. SSD will improve the speeds provided you have SSD on your laptop/desktop so that it can send data QUICK. also any wireless backup will depend on your wireless router.
How old is the phone? And are you a 'constant' user or a 'rare' user of the phone? If you are 'strong' user then heat + quick discharge is a sign of weak battery. Just read one of the manuals here in ifixit and replace it...Samsung Galaxy S7 Battery Replacement