Rear wheel not moving when axle nuts tightened
It sounds like the freewheel is hitting the frame. Can you see any contact between the outer cog and the stays?

One possibility is that you dropped a spacer from the axle as you put it together.

Another is that the freewheel might not be threaded all the way back onto the hub and you should hand tighten it.  The first few pedal strokes will tighten it the rest of the way.

It's also very easy to get the freewheel cross-threaded onto the hub, which would keep it from going on all the way.  It might be possible to take the freewheel off and get it restarted.

In any case, a picture would really help, especially if it shows how much the locknut protrudes past the freewheel body.