Well I'd really love to give you more information on my brother's training cycle, but I don't know it unfortunately--it is written up week by week on the board at the gym he is at, so neither he nor I know what the plan is until that week lol. Only the coach knows! Typical russian....
Anyway, that's good progress on your lifts. And you're right, mobility work is EXTREMELY important to be able to handle the repetitive lifting. I am convinced that is one reason why people who otherwise would physically be able to recover from the frequent style of training do not, proceed to get injured, and then say that it's not going to work for drug free trainees.
mobilityWOD is a GOLD MINE. I love K Star, great resource. As far as the high rep back off set, man just try it and see! If it works, then great. It may help add more muscle, you never know. If it doesn't work, drop it and go back to what you were doing. I wasn't intending to stop you from that--I misunderstood what you were saying and thought you were going to go to an 8-10 RM for your top weight sets.
Your calorie increase is probably going to blow your mind too. You've been so adapted to lower calorie lifting it might really help. I would second one of the above posters and say check out the Greg Nuckols article on daily maxing if you haven't already (I think it was posted up late last year IIRC). It seems you are doing pretty much most of the things he was, but it might give you some other insights as well.
A couple things I might suggest you think about trying: 1st, alternate front and back squat days. I think it might help your upper back and quads especially if you are not pulling much heavy weight in the deadlift. Not necessary at all, just a thought. 2nd, consider doing a single assistance exercise for your weakest muscle group on the bench press after your singles, something like 3 sets of 8-12 just to move some blood in there (like Sheiko's program calling for dumbbell flyes). Nothing near failure or hard struggle obviously. I would take similar guidelines to Thib's NC workouts almost. I would not do this for the squat. Only 1 lift at a time IMHO, at least for as long as you can get away with it.
I would also add them in only once a week--at the end of your week like saturday-- for the first couple weeks since you are still getting results as is. Then 2x a week for the next few weeks. Maybe keep it there or maybe increase to 3x a week. I don't think you need to be going any higher than 3x a week, and 2x will probably work well over the long haul anyways.