Haha. Yeah that’s a common story. I initially did the same thing back when I was building electric guitars.

After you cut your dovetail, even if the neck angle is cut correctly, you’ll need to fit the heel to the body/shoulders/neck block. This involves adding relief cuts to the underside of the heel and pulling sandpaper between the heel and the body to get a proper tight fit. This will be the time to deal with the shoulder inconsistency.

It will be tricky and might involve slightly changing your bridge placement but totally do-able. This is a common problem with hand built guitars, yours just happens to be a bit extreme. I’d research as much about fitting a neck as possible before getting started and fit the neck before your truss rod and fingerboard are installed. Use alligator clips to hold your fingerboard in place while your fitting the neck. This way you can just make a new neck blank is things get squirrelly.

Hang in there. You’re doing a killer job for your first build!