Since Red Jacket is now owned by ITT, I'm not sure who's cheap tank they are putting the Red Jacket name on. I can tell you that neither ITT nor Pentair who own the other half of the brand name water products have a decent tank in my opinion. There are only two very good bladder tanks on the market today. They are Well X Trol and Flexcon. So far they haven't been bought out by any large conglomerates. (At least as far as I know)
I tend to agree with your theory that the bladder has ruptured and water is on top of the bladder but not yet high enough to come out of the schrader valve. There is probably very little air left in that tank and I assume you noticed that when you let the air out. If it were pre charged like it should be with a good bladder, it would take at least ten minutes or so to let all the air pressure out of the tank through the schrader valve, depending on tank size.
You need a new tank for sure. If for no other reason, it's already quite old.