I tried the same 50 lb ft then back off procedure once on a wheel bearing years ago and it burned up in short order. I really think the 50 lb ft is just too tight for what we're trying to accomplish.
That being said I now grab the center nut with a channel lock pliers and tighten it tight while rotating the hub. Then without rotating I back off and hand tighten. By hand tighten though I mean just grabbing the nut with my fingertips and tightening it down until it stops. If the nut winds up in a position to where you can't lock it down, always loosen it slightly to align it, never tighten it.
On your trailer I would probably repack the bearings again, then leave the nut one notch looser than you did before. Drive the trailer around the block then jack that side up again and with a hand on the top and bottom of the tire (12 and 6 o'clock positions) see if you can rock the tire in and out. If it has no play or extremely limited play I would run it like that.
