I used this exact fluid about 80,000mi ago:

https://www.amazon.com/Red-Line-50304-Transmission-Transaxle/dp/B000CPCBEQ?th=1

Which reminds me... I should probably do it again for maintence.

Your flywheel is going to be fucked from driving so long with a slipping clutch. Shame on you OP for driving that long like that. You should replace that shit when it starts slipping to avoid damage. Your bell-housing is probably dinged up on the inside too. You're gonna want to drain the trans oil and inspect it for metal flake and then when you replace it (assuming there's no metal) you should probably go with Red Line MT-90.