Turkeys won't cross anything if they don't like your setup.... But they'll cross everything if they do. A large majority of the places I hunt have big creeks or rivers on them, and I consistently call birds across water or across fences and call them into range. This past Tuesday, I called 3 different gobblers across a big creek, with steep banks, right into the decoys. Unfortunately, I managed to miss every single one.... Turkeys live in the wild, they can't just not cross fences and water..
Calling really depends. If you can't call very well, you're probably better off not calling much. If you can call, I don't think you can call too much. A lonely hen in the woods can make a bunch of noise. When I'm running and gunning, I'll call quite a bit, but when I'm in a spot where I know birds work through often, lots of times, I'll call very sparingly.
It's been my experience that birds that live in more open areas talk a lot more than the birds do in the big timber areas.
Regarding your bird that hung up at 60.. Did you have a decoy? Were you in an area where the bird could see a long way? In the turkey world, hens are supposed to go to the gobbler, so if you aren't using a decoy, sometimes it helps to put some terrain in between you and him, to force him to keep coming to look for you.
As far as how often to talk back to a bird that's gobbled at you.. That really depends. It's all about reading that particular bird. Most of the time, when I know a bird is specifically gobbling to me, I'll respond to ever 3-4 gobbles for a few times, and then just shut it down and wait for him. He'll almost always come in, and it'll be quiet.. Listen for him to start spitting and drumming, and then he's toast.
Other times, usually in areas where the birds are more talkative, they want you to yap at them all the way into your lap...