There are also plenty that are sound with no prior injuries. Not worth the risk
Not ideal as there will be a lot of pressure on those areas whilst jumping
Honestly I wouldn't get in to the knee chips issue. Been there done that. Knees are very important for jumping! After it is chipped, one little thing could break it off again especially with all the pressure from jumping on the knees. If you are stuck on adopting an ottb, I suggest to get something with more minor issues.
It depends how they recovered. My older warmblood bowed his tendon and it took me eight months to get him back to full recovery and a 1.40m fence was not a big deal for him
that's a huge risk. not one i would take personally