Ok so I have an update and somewhat good news....
The guy I bought it from said he changed the hydraulic fluid with ISO 46.....which is a no no for hydrostatic.
So I changed it out, twice, with Traveller premium universal tractor fluid which is for hydrostatic use. After talking to someone, I put all four tires in the air and worked the hydrostatic in both directions for at least 5 minutes. This made a very noticable difference in operation.
After that the tractor operates much more smoothly. Forward direction seems normal now, reverse is slower as expected. I do suspect the hydrostatic pump is a bit worn but will probably serve my needs for a while and I will eventually rebuild it.
I am going to change it out again in a month or so. I drained it and filled it, ran it as mentioned and drained it again. That ISO 46 is too thick and foams so that definitely explains the issues to me.