Respectfully, I'm trying to understand your problem but your diagram is showing the wrong end of the sprit (if I'm understanding the problem correctly). If you're getting "two-blocked" on the fwd end,and no amount of moving the blocks fixes it, you may need a longer sprit.
On the front of my sprit I lashed on a block as shown in the photo, I could have made the line holding the block much shorter.... not sure if that helps. What I did here is make a loop of line from amsteel by tieing a diamond knot, then laid the loop on the spar and lashed that line down with lash-it, of all things, putting the diamond knot on the far side of the lashing so it would bear up against the lashing. I think I used 3444 from ABOK.