I would just add that there is wai (external) jin and nei (internal) jin. they are not the same externally i would agree with what you have said "jin = li (muscular force) + qi (ki)" internally muscular force should not be used. li (muscular force) can be broken (like a stiff piece of wood) true jin is unbreakable (like a fast flowing river).
That's in line with some of what I've felt from some high-level people. I know the few times I've been able to do anything, I didn't feel like I was doing anything at all. But the li + qi is the only definition I'd read.