300 lbs? I went from 320 to 152 in 6 months, I'm back to 198 now. During the summer I can get into a size 30/32 pants, winter time size 34. I was pallbearer for some fat friends, it hurt and I said I wouldn't be a burden to others.

Looking at your trailer/steps. Hitch in front and boat behind for directions. The plate on the right side could be longer. A piece of metal cut and welded at an angle to support the bracket on the left. A stop would need to be welded to the bracket.
The trailer Y's out. A piece of angle iron to sit on that frame welded to a piece of angle iron or square tube, welded to the step bracket.