A few thoughts....

You shouldn't need to pull the halyard while the mast is rotated. Pull up then rotate and then relase tension on halyard.

If you have the type of halyard ring with a small eye that the halyard goes through with a stopper knot, have the knot on the stern side of the ring.

Tip the boat backwards on the launching trolley [Stern down]

Have about 12 goes at getting it down, scream and cuss. someone else will come over and do exactly the same as you were doing - it will come down 1st time!