First of all, nothing you said so far points to a serious safety issue as far as driving the vehicle. You are WAY ahead of most people by knowing how to open the bleeder screw on the brake caliper to relieve trapped brake fluid, but we have to figure out why that is happening. What I'd like you to do is get a special wrench called a "line wrench" or a "flare-nut wrench", that fits the soft metal line nuts on the master cylinder. You won't know the correct size, but if you stop at any auto parts store, they'll pick out a few and try them, then sell you the right one. Have them point out the brake master cylinder and the two, (or four) steel lines coming out of them. This line wrench has more sides than a regular wrench. A regular one usually rounds off the six sides of the soft nuts.
The next time the brake starts to lock up, instead of relieving the trapped pressure at the caliper like you have been doing, loosen one of those line nuts about a half turn and watch if any brake fluid spurts out there. If the brake is still dragging, try another line nut. Oh, and don't forget to retighten the nuts before you start driving again.
Now here's the clinker. We hope this trick does NOT work, and you have to open the caliper's bleeder screw again. If the trapped brake fluid releases at the master cylinder, it's almost certain the brake fluid has been contaminated with a petroleum product. That will make all the rubber parts swell and get mushy. The fix for that is REAL expensive. I'll elaborate on that if it comes to that.
If you do have to go back to the bleeder screw, we'll figure out where to look next for what's trapping the brake fluid. A constricted rubber flex hose is a good suspect, but you have an anti-lock brake system hydraulic controller too. Those don't typically cause this problem, but they could. That could be related to the high-pressure pump failing to turn off, and that sounds like what was unplugged. Disabling that system leaves you with the "foundation" brakes, or base brake system like every vehicles has had for almost 100 years. You've disabled an optional add-on system, which means you have to be in control of preventing skidding. You can't rely on the anti-lock system to do that for you.
The shaking is due to a misfire. Normally that's due to worn spark plugs, but on GM vehicles that can also be due to mismatched injectors on high-mileage engines. The place to start is with new spark plugs, and a set of new spark plug wires if your engine uses them. I'm sorry I can't help with the other issues. I can help with the brake system, but for the other things you might consider posting a new question related to those things. That way the other people will get to see it and be able to respond.
Wednesday, August 26th, 2015 AT 11:33 PM