PTOs are plenty durable. I mow stuff that's too big for my tractor. If I can get it bent over and under the bushhog or tractor I will slowly mow it down. You don't hear about many failures of these things. The back PTo can be taken out as a unit from the back so anything that needs to be replaced is easier I am sure than on some tractors. you still need tools and know how, pullers and presses but you can get these things apart. That said I have not heard about a bad bearing really that I remember let alone a busted gear??
They easily will till and bush hogging is probably more of a stressor. Especially when encountering things like small trees etc.
As for weights what ever you can get the cheapest to hang up there. There all about the same. some have had luck buying at like lowes for their yard tractors. I just have a solid metal bar that's 3"s and a 3" ID pipe filled with lead on the front of mine to make a 2 pipe front pipe bumper on mine. Welded to some brackets made from just angle iron.
Awesome, thanks for the info!