Congrats on your repairs to date. I did some of these same things on my 6 volt tractor recently and it now starts up just like my 12 volt ones do. Very cool, indeed, when everything is just right.
As for your gasket: Try some sheet cork. Trace the glass bowl and then cut out a ring a little larger. You should be able to find good gasket making material in any auto parts store or a hobby store.
Good luck and let us know how it goes, OK?