A picture of the carb will help.
On most carbs I've worked on, the main jet is located in a protrusion coming down from the carb body into the float bowl. Look inside the protrusion and see if you find a small brass fitting with a tiny hole in the center and a slot across the surface. If you do, that's the main jet. You need a proper size screwdriver to get it out. If you use one that's too small, you'll end up with a damaged slot and possibly not being able to remove the jet.
You can try leaving the jet in and running a very thin piece of wire through it. I like to use trash bag ties with the plastic or paper removed from the wire. That's thin and flexible enough to get into just about every orifice on the carb.
When you put the float bowl back on, it seems you didn't have the gasket properly mounted. They're pretty thin and tend to twist a bit. Take the float bowl off, straighten out the gasket then put a smear of grease around the carb body where the float bowl gasket sits. Gently push the gasket onto the greased surface and ensure that it's laying flat. The grease should hold it in position while you carefully install the float bowl.
Certainly you jest that the gas treatment/stabilizer didn't work!
Blasphemy!!!
Stop using that junk and drain your fuel tank and carb at the end of each season. It will go a long way to prevent carb problems. If you're using last years fuel and it doesn't smell like fresh gasoline, siphon the fuel from the tank and put in some new gas.