I have very rarely if ever heard "forbad", and I think many people in Canada would agree with me that that prununciation is a little precious, somewhat like pointedly making the future tense with "shall" (especially when the meaning is clearly one of determined intent!).
Though it's clear enough that "forbad" was once standard English, and was even spelled that way, I should think it's a regional pronunciation today, like "cla(r)k" for "clerk", or perhaps "forbaid" if "forbad" is still the standard in the UK.
"Forbad" puts me in mind of Pope's couplet
"Here thou, great Anna, whom three realms obey,
Dost sometimes counsel take -- and sometimes tea!"
It somehow seems from that era.
PS. Please don't take offence at my blunt word "precious" above. Reaction to slightly alien pronunciation and diction is automatic; I imagine lots of things about new-world English sound odd or even laughable to educated British ears.