Unlike the last days of WWII, neither side has the upper hand and therefore the idea of Polish forces defecting to the winning team is irrelevant.
Yes, the 5th was seemingly out of place, but I believe I've already addressed this in
http://forum.juhlin.com/showpost.php...5&postcount=14 Same goes for the 8th.
Reset was an SF operation. The unit tasked with it's retrieval were using the 5th as a cover and unofficial escort to the area before splitting off and entering Lodz on their own. B Coy, 116th ACR were another "parasitic" unit tasked with meeting a contact in central Poland (which they never did) and receiving further intel and orders for their mission (recovery of the Black Maddonna - a mission they still don't know about months later).
We have indications in canon that the Soviets mounted a counteroffensive. We also have clear indications that the US XI Corps was cut off by this counteroffensive. As the XI Corps was the spearhead, it is not unreasonable to assume the soviet thrust split the III German Army in two - the XI Corps to the east and everyone else to the west.
The Soviets undoubtably devoted a sizable force to this thrust. I think we can safely assume at least an Army of 3 divisions (which ones I'll have to check later when I'm home), but probably consisted of as many units as they could muster.
Realistically, the XI Corp was not overextended
according to the plan, however due to hold ups in northern Poland and the soviet counteroffensive, the follow on units for the 5th ID never made it, stranding it hundreds of kilometres from friendly lines, the 8th ID moved too far and the 2nd MARDIV, not to mention the rest of XI Corp, pulled back from their easternmost positions further increasing the apparent overreach of the two infantry divisions.