Nice engine. Nasty looking banjo bolt - you are lucky it didn't snap!
Now you have it looking nice and running...and then it seems the heating
element died or is dying. Have you checked the resistance with a meter?
First, in any event, the rivets need to go. I replaced them w/nuts-n-screws
of a size that fits well. Good enough for me. The next owner in the distant
future can install the rivets if they want. It's why they call it a hobby and
not a job. You only have to please yourself.
If it really is dead I strongly suggest buying another Jensen heating element.
Keep it original.
If not an original, look thru ebay listings for various heating elements. I've
found success with cartridge types (properly buffered) mounted under horizontal
boilers (Empires) and cylindrical 'pipe warmer' types for vertical boilers (Elektro
and Empires).
Good Luck,
Wayne