Hi Matt
I really sympathise. I am in my 40s. I did my ACL in the 80s, reconstruction in 90s [patellar tendon] which worked. Then last Oct playing football with kids slipped and ACL went along (or failed in the MRI report) with both menisci torn. Gutted about it but life goes on!
I have had some good advice from people here, esp Kaputt_Knee. Also came across this link
http://www.kneeguru.co.uk/KNEEtalk/index.php?topic=62219.0Like you I don't want to play football or run but want a knee I don't worry about. On rehab route & going to explore ACL revision from autumn.
In terms of coping without an ACL rehab has gone really well. I got a physio who was really interested in my recovery. I started with the basic exercises and balance stuff (which you will be tired of I imagine) and then a lot of Swiss Ball which are tougher than anything in a gym. Physio told me that the hamstring can alleviate the loss of the ACL, at least to some degree.
Swiss ball has developed massive hamstring power. Now I am pretty much there with stability and feel confident with the knee.
I do 3 times a week on the leg routine at home and am progressing it with levels of difficulty, (an hour or so including 10 mins stretching at end), bike 3 times (started on the recumbent in gym and outside now). I get to the gym for some other fun stuff to feel normal (rowing, cross trainer & do some basic leg machines).
Your meniscus may be a problem with twisting etc and I don't know about HTO issues.
Good luck and hope it all works out.
Joe