OP, I think you last posted over a year ago so it probably won't help you - but I think the calf muscle is the right muscle to be targeting.
Someone else last year mentioned "Prolonged stretching" and that is what totally cured my plantar fasciitis. The key is that you really have to hold the calf stretch a VERY long time. Far longer than you think you should.
The theory is that if you hold your calf stretch for over 2 minutes (past what they call the stretch reflex which is the sense you get that you should stop stretching), it sends a message to your body that the calf muscle needs to grow longer! If you repeat this stretch, for at least 2 minutes, for 4-6 weeks, eventually your body actually starts growing a longer calf muscle.
Or the tendons. Or something. Something that needs to grow longer, grows longer. All the other strategies try to mimic this same thing, really. But all you need to do is a simple stretch, but just HOLD IT for two minutes per leg, and do it for at least 4 weeks.
This is what worked for me:
https://www.youtube.com/watch?v=RRDC8erSNqw