Flipping axles is the proper term. Its coined when all trailer axle tubes were straight. FYI Some trailers today have straight axle tubes so simply flip or rotate the axle and take the brake backing plate off and rotate it hence flipping the axle. If your axles are straight and not camber bowed then the job is simple. There will be no added stress on U bolts from flipping axle on a single axle trailer.
The tires are fine. As some mentioned small diameter tires rotate at a faster rpm and require more attention to good bearing maintenance.
Your experience with the V6 engine is typical when towing or carrying weight.