This dude will have to take on double teams freeing up the LBs. Strength should be the highest PA IMO. What PAs come next? I'm thinking Agility, Vision, Stamina, and then tackling.
Basically, say "Screw You" to everything but Strength, Stamina, Vision, and Tackling. You don't need agility or speed, you're not moving. Strength should be the definite first priority, getting to the 3rd soft cap(the one after 60, I believe it's 68). Then, work on the Run Stuffer SAs. Wall is going to be KEY in the 3-4. Definitely pour points into it, getting it up to 8, if not 9 without custom equipment. Vision is probably the next important stat, as you HAVE to be able to see if the RB is coming your way and adjust accordingly. Vision should probably go up to the first soft cap for a 3-4 NT. If at any time you notice a considerable amount of energy loss or missed tackles, increase STA and TAK accordingly.