That would be the intermediate shaft. You sure you're putting the proper side in? The end with the threaded hole should be pointing towards the right side (disconnect side). Should take more than hand pressure to push in.
Yes, the threaded hole is facing the passenger side. I can push it into the seal fairly easily, just cannot get the splines to mesh. I will work on it again during the day, maybe get my son to turn the driveshaft while I try to seat the shaft.
I don't remember it being any big deal when I replaced my disconnect. It stuck in the disconnect seal and came out when I pulled the disconnect off. I put it in the disconnect the same way it came out and put it back together like that. I don't even remember having to turn it to get it to seat. This was only about a month ago.
The disconnect actually isn't the issue... it's getting the shaft to fully seat into the differential. I had the diff out to remove the oil pan but the shaft doesn't want to go into the splines of the carrier.