T210R not flashing ROMs via TWRP

I was rocking an old S.E.A.L. ROM for a couple years until it started becoming unbearable due to apps crashing and random reboots. So I downloaded a couple new ROMs to try, along with a new kernal, and put them on the sdcard storage.

I did a factory reset wipe, and tried flashing with TWRP. Couldn’t seem to run the install properly and kept getting corrupt file errors.

So I used ODIN to update TWRP to 3.0.0. I tried all kinds of flashing again with the same errors. So I re-downloaded the zips and moved them to ExternalSD. The flashing process now seems to go smoother, but the problem is that it doesn’t seem to actually write anything to the device. However, I did flash the latest SuperSU zip and that seemed to create a folder, etc..

I tried using ODIN again to re-flash the recovery (to try TWRP 2.8.0) and that seems to fail now. So it appears I’m stuck with TWRP 3.0.0. I can boot into Recovery and Download modes no problem.

I’ve tried just about every approach to ressurect this tablet with a fresh ROM and nothing is working. My head is approaching the explosion point.

I’d appreciate any advice!
Thanks!