I think we've all been down that road. When it comes to electrical issues, I use the KISS rule that an instructor told me years ago. Keep It Simple Stupid. It seems to work pretty good. Glad you got it fixed.
When it is hot , turn it off and remove breather lid and see if gas is leaking into intake. It will be smoking if it's leaking. Does it ever try to keep running when you turn off the ign?
I've found in some cases, it's easier to break the steel line loose and then take the adapter loose from the case with the steel line still attached. The adapter is easier to get e wrench on.
I'm sure it's all broken down somewhere. Not saying u have to use synthetic. I think it's more of a preference thing. There should be some advantage to using it.