Wow! That looks a lot like my dump trailer that is titled for 3500 pounds.I had to sign up just to answer your question. I just bought a trailer about 3 months ago to do the same thing you requested. It has been working great.
I chose to go with a single axle trailer so it wouldn't tear up the grass as much in the yard. If I wasn't worried about the yard, I would have gotten a 2 axle trailer to distribute the load.
What I found was this Delco 5X8 7K dump trailer that is really heavy built. I pulled it all around my yard to pick up limbs after a recent ice storm and it worked great. Also used it to get sand and haul fire wood, my tacoma pulls it great. I haven't tried to load my tractor in it, if it fit it would be tight and the loader would be hanging over. A 5x10 I think would be the sweet spot.
I need to post a picture for comparison. Mine has an aluminum dump bed and electric brakes on the axle. I should see what the axle is rated for...but think that is the limiting factor as for weight rating. My frame is box tubing rather than channel, same as yours seems to be.
Also pulled behind a BX a lot. With hills I think 5x8 is the limit for me behind the BX.