Oh oh! if you've split the helicoid and not marked where things were when it came apart then you're in for a bit of fun...
Your main problem is the front part of the helicoid - the one with the coarse thread (the one the front lens group is screwed into) is in the wrong thread and is not going back far enough into the lens body to allow infinity focus. You need to take the rear mount off, then unscrew the front helicoid, and restart the helicoid one tread to the right, then reassemble.
You may need to do this a few times, as you amy also need to adjust the rear helicoids position (the one with the fine thread) around 1/5th of a turn each time until you get it in the right position.
The right position is one where the aperture unit is in the right position so yu can screw the rear mount back on without the aperture unit being tight, and that allows you to focus the lens to infinity..
I hope this makes sense?? If not send me a PM and I'll try to answer your questions