I would add a block on the inside, probably a 40mm Harken, on the top becket where you currently end the line. Then add a tie point by creating a loop of 3mm dyneema through the center of the bottom 3 blocks, and attach the end of the line there. Working inside keeps all the loads down, except for the external block fittings, which are designed for the high loads.
Also, you should reeve the line with the top and bottom blocks perpendicular to each other, not parallel. That makes it easier to avoid crossings