If you have a factory tilt column a substantial amount of play can develop there. The u-joints inside go to crap sometimes, most likely from a previous impact. I don't really have any idea how to eliminate this problem; when mine went silly, I cashed it in on EBAY. Even in fair condition, they go for a mint
The other big culprit is the control valve.
If you haven't rebuilt your c/v, consider either, a REPUTABLE rebuilder, or buying a new one.
If you want a permanent solution, rebuild everything that isn't recently new; I would not start with the box. From what I can gather, in your case, that would mean idler arm, C\V, pump, lines, and the inner tie rods. Use moog parts, Rockauto is real cheap there. If you still have play at that point, replace the box. Borgeson seems to be a reputable and reasonable choice.
Unfortunately, piecemealing your steering situation is going to likely give you piecemeal results. So consider your investment. My solution was more radical, do what you think is appropriate.
Good luck