Thank you for clarifying regarding it being upside down! Aside from heat, is there a recommended rust penetrant I can use? I've seen recommendations for PB Blaster, Kroil, etc. but I'm looking for the cheapest but most effective. WD-40 is a no-go lol.
Transmission fluid is good as a penetrating oil plus mixed with a little lacquer thinner or finger nail polish remover is claimed to be the best. The connection is stainless nut to stainless threads to you shouldn't have any corrosion just tightness.