Biking does not replace easy running. Sure, your heart and lungs are doing their thing. But they are not doing their thing while the legs are getting used to pounding and your stride is getting more efficient. You can only get that by working on running. The boosts gained from cycling are minimal, and I'm guessing you've probably already gained most of what you could in that area.
I'm thinking 1-2 years of getting solid running mileage in will allow you to see really big improvements. I think it would be another 2-3+ years on top of that of slowly increasing miles and/or intensity, working on races, etc. to get closer to reaching your genetic potential.
As for injury proneness, you really just need to do three things. 1, slow down most of your runs while you're building mileage. You will often feel good from the increased running practice and the small, regular bumps to your fitness. Don't exploit those. Test them in races from time to time, but keep your training slower and easier than you think you need to. 2, anytime you feel a little niggle or bother come up, work on it. Take a day or two off. Get a massage. Get some new shoes. Whatever, but don't let it become a bigger thing. And don't just run through it without changing anything. Lowered mileage for a few days or a week is nothing compared to lowered mileage for months cuz you got hurt. I know, I've been there. 3, get on a core/hip/general strength routine and stick to it. Also work hard to identify your problem injury areas and add in new exercises to protect and stabilize those.
A lot of people will look at runners consistently cranking out 80+ miles a week and think, oh, I'm injury prone and don't have the background to do that. No, you haven't put in the time and work to do that. You haven't earned those 80+ mile weeks. It's certainly true that some athletes are more gifted in some areas than others. And naturally good biomechanics and strong bones and tendons will mean less injuries for some. But I truly believe that given enough self-reflective attention to ones training, pretty much anyone can pile on lots and lots and lots of miles and make huge improvements in the long distance races.