Avoiding Injuries and Staying motivated after multiyear break

I (primarily) sport climbed outdoors on fingery limestone for seven years (age 17-24, about 4 days a week) and built up to red pointing five thirteens. I had a few nagging overuse finger issues (achey and painful but never diagnosed) that were starting to hamper my climbing. I plateaued and then quit climbing. I did manual labor for 5 years or so (grabbing tools, ropes, etc.) then quit that and have not been continuously stressing my forearms or fingers for a couple years. I am starting to climb again but am being  cautious so that I don't hurt my fingers. However, my mind wants to climb 5.12, my muscles want to climb 5.11, but my sinew (tendons/ligaments) can only handle 5.10?. My questions are who else has had this experience, how did you come back and regain strength and/or sinew? What did you learn from this process? Did you do anything specific to prevent overuse or acute injuries? Did you have to start from scratch building sinew strength? 

Currently, I am coming off a couple years of endurance sports (no forearm strength!) and am 31--starting to see wrinkles. I have two weeks of ARCing at a gym a couple times a week for a total of 30-60 minutes each session staying off tweaky holds or anything over V3. Climbing outdoors on 5.10s for mileage (500-800') once or twice a week. And my third week on I just did a very easy beginner hangboarding session, pulling up to half my body weight off to keep it conservative on some of the non juggy holds (no tiny holds). My thinking is to start to stress the sinew conservatively and slowly early on so I can start to see adaptations sooner rather than later. I will start taking pre work out gelatin and vitamic C starting soon, as Eric Horst as some researchers claim a 50% increase in sinew growth with it. My fingers feel a little achey (especially the ol overuse injury joints) but mostly OK. I plan to do a full 4 weeks of fingerboarding slowly increasing weight and maintaining a good bit of ARCing as well-with 48-72 hours between fingerboard workouts. Then If I am feeling good, allow myself to boulder  for two weeks (V4-V5?) and work on power-endurance on steeper sport climbs for 4 weeks (aiming for easier grades, juggy 5.12-). I will probably continue to ARC easier routes throughout and continue to be aware of and work on my "climbing route pyramid". After about 16 weeks on I plan to take a 2 week break to re-asses. I've never trained systematically before (or hangboarded or climbed indoors) and I got these ideas from reading RCTM by the Anderson brothers. Am I on the right path? Overly zealous or conservative? Where am I going wrong?

TL;DR

After a multiyear break, how fast do ligaments and tendons degrade to their preclimbing state and how have you dealt with building them back up while continuing to improve, stay motivated and minimize risk?

Edit and Update:

In case someone is in a similar situation, I feel as though I should update. After three weeks of easy climbing, I developed a swollen ring finger presumably from overuse. Almost no pain. Likely tenosynovitis (swollen tendon sheath) near the A2-3 pulley. I went to a sports doc and she said capsulitis (a close cousin of tenosynovitis) and not to be too concerned, just keep doing massage, stretching, icing, NSAIDS, and non loading bearing mobility exercises like I had been doing after injury. However, in One Move Too Many the doc suggests tenosynovitis is the worst vicious circle a climber will face, so I am being very cautious (haven't climbed for a week, even though swelling is down) incase that is what it is. However, light amounts of stress and mobility seem to be important. And if I could start over, I'd start by easy climbing 2 days a week on easy terrain and do PT on my hands as if I was recovering from injury for at least 2 months. This is becuase my hands were likely injured in the past and probably have all sorts of scar tissue, sinew cross linkages and under the surface issues that are hard to pin down (especially since my pain threshold in my fingers is lower than in my forearm for example, test yourself by pinching non calloused fingers and forearm). I am going to reframe the entire season as primarily injury prevention, education and climbing mobility to slowly test and adapt to the rigorous demands of climbing. Yes my muscle is growing back fast (becuase of my previous levels of fitness), my mental and technical are also coming back quickly, BUT my joints need a lot more time and care.

Update: A year and a half in of cautiously loading fingers and listening to my body I am feeling resilient. I just concluded two 5 week cycles of hangboarding near ~70-80% intensity and took a lot of rest in between sessions, climbing minimally. I am also able to push grades to my younger self's ability. Bouldering v7 and 2-5 go redpointing 13a's and onsighting up to 12cs. This has been a huge journey coming back from such a long break but with some care to your loading regiment it is totally possible. And all having done this without any major injuries. If you're in a similar boat, know that its possible and feel free to DM me w any questions about process. Major takeaways are: lots of rest, listen to your body, be consistent, strength train, mod-vol volume combined w mod-high intensity. Cheers and happy climbing.