Well, I finally got it completely assembled. It took 2 people(one holding the front of the gun) and myself hitting the trigger group into place with a wooden mallet(with a cloth over the trigger group to prevent damage).
I have done something similar to what you said before too(that was the first time, and the magazine fell out too, because I was not locking it into place
). I believe that I positioned the front of the barrel so that it was touching the wall to prevent movement and maximize force, while laying the rifle on the ground with a cloth underneath as suggested.
I can say based on the my experience, the advice gotten, and videos that I have seen that the trigger groups of these weapons can definitely vary a lot. With some, they seem to lock into place with very little force applied, some take a little more, some more still, and some feel almost impossible to lock in without the use of tools such as hammers, etc. I even saw one video where the guy someone managed to lock the magazine and trigger group in with the bolt attached.
I also kept reducing the force of the hammer strike as I did not want to damage anything, which meant that the trigger group would not go into place fully.
So, I think in conclusion:
One's SKS might be different than mine, and have the trigger group lock in easily; or, as runningman described, you might have to file off an extremely small portion of the magazine(which obviously should be done only when the other options definitely won't work). Or, it might be similar to the experience that I had, in which case you should not expect something other than applying massive force to the trigger group to lock it in. Also, do not hesitate to wipe down the trigger group, magazine, and their holding areas a few extra times to try to get out even just an extremely small amount of dirt/dried cosmoline/whatever(this applies even if you had already cleaned them as I did; sometimes even a few infinitesimally-small bits remain and can hinder the parts locking in). This was runningman's advice, and following it my magazine went into place when it previously wasn't; this could also help with the trigger group, if whatever space that grime is taking up is preventing/making it more difficult for the trigger group to fit in and lock in. When it is said that these guns have tight fits, it is definitely true!
Thank you runningman once again for the help!