I think the biggest thing that you could do is to set up a timeline that summarizes the events. I've been taking bits and pieces of this timeline's history, but it's been difficult, and I think it'd be great for future discussion if you could put one somewhere, like the OP, for example.
As for the Hungarian borders, there are disputes on historical Hungarian demographics, but the general consensus is that the current OTL Hungary's borders were always primarily Hungarian since the Magyars moved in there. As to whether the Ianyaens could have taken it during the 1500s would depend on how Ottoman expansion in Europe went.
Anyway, it just seems weird that Russia would have taken Eastern Galicia-Lodomeria and yet have Poland and the Baltics independent. Of course, A-H might not exist, or be somehow different in this timeline, but at least based on OTL, it would seem much more likely that Russia would have tried to secure its existing territory (especially the Baltics due to its proximity to St. Petersberg), and I doubt that the Germans would have so willlingly let the Russians take a bite of A-H. If you really want to keep the current borders, perhaps you could make it so that there was some sort of conflict post-war between Poland and the Ukranian population there and Russia intervened afterwards?
As for Polish borders, I suppose there is always room to make considering this timeline seems to be significantly divergent from that of OTL, but I'm really curious as to whether the Entente would have had the capability or the will to force the Germans to give up the corridor. From what I read earlier, it would seem that France suffered some sort of socialist revolt during the war, or perhaps after it, I'm not sure, but it appears that they had a lot of internal issues (the French were barely inches away of running out of supplies and going into starvation before US aid arrived OTL, so I'm assuming that if it was worse than that, it was really bad).
A more likely proposition, if you want to keep the corridor, would be that Poland fought against Germany to take those lands by force, and that the weakened post-war Germany couldn't stop it, although I have to wonder just how much Poland could have messed around with the Russians at their backs.
As to whether the terms were too harsh to Russia... that's for you to decide, I suppose. I'm not exactly sure what the hell went on over there, so no comment from me at this point.