Wow, ok that was very difficult to understand. You need to sort your information better so we can help you.
- Your distributor gear drive sheered off, and you guys installed a new distributor. Everything ran fine.
- Lately it's running rough, backfiring, poor or no idle. Tried adjusting the mixture screws on the carb and got it running fine.
- Replaced plugs and belts (no change)
- Found vacuum leak (hissing). Found loose hose, installed but now will not start at all.
First, I don't think your distributor is the problem at all. Sounds like it failed (fatigue), got replaced and is now good.
You probably developed a vacuum leak, causing your poor idle and backfiring. Vacuum leaks lean out the mixture.
You compensated for the vacuum leak by turning out the idle and main jet screws.
Leak got worse (hose fell off completely?), you found it. Put the hose back on, and now you're running super rich. Flooded engine, now won't start.
THIS IS ALL JUST THEORY.
My suggestion is to cap off the vacuum leak at the back of the intake. Do not put the random hose on it... you don't know for sure that's what it's there for. If you post a picture, we can try to help you on that later, but for right now use a rubber plug or duct tape over that nipple for now.
Put your mixture screws back where they were. If you don't know how many turns you moved them, the very
rough setting for most carbs is 2 turns out from bottom. This means gently
screw both mixture screws all the way down until the bottom. I cannot stress gently
enough. That is now your Zero point. Turn each screws out 2 full turns.
You've monkied with this one pretty good. Hopefully you can get it close on your own or you may need to pay a mechanic. Talk to your grandfather about where to set the mixture screws if he's available.