You're in over at my board.
It would be best to address the chronic injury, IMO. I really don't follow the rest of your question entirely. If you can safely perform an exercise, I would do so. MR's (per the book and that video) have the limitation that you need to be able to safely take the exercise to failure. Also, you'd be starting and stopping between the sets of the MR, so an exercise where that's an issue (injured or not) is not a good choice. For instance, OH DB presses, unless you're using powerhooks or a similar set up that keeps the DB's at the starting position between sets, aren't usually a good idea (for MR's or most any cluster set) b/c of the energy expenditure in getting the DB's into position.
Working around an injury / physical limitation is a very specific endeavor an depends on the nature of the issue. I'd not even try to give you any specific advice in that regard without knowing exactly what you've got going on, except to say that seeing a professional and trying to fix the issue at it's root if at all possible before trying to push into progressive overload based training is the best course of action, IMO.
As a side soapbox, we have a culture online of trying to deal with orthopedic / neurological issues online (various kinds of discussion forums) and sometimes that will work, but in general I think its not terribly wise to try to get what is essentially low low level telemedicine (text messages only in many cases) often from non-licensed individuals to fix these kinds of issues. It's totally reasonable for someone to want to reach out this way - it's just soooo common - but not the best route, as far as I'm concerned. (Yes, sometimes doctors and medical professionals can be shitty ass clinicians, but there are a Lot of good ones out there!)
-S