wow... sounds complicated...

as others have said do you really want to *know* the truth? Perhapse one day you will, but if you are happy not knowing at the moment why pull all that stuff up and put yourself through it unnessiserially?
If it was me I think i'd want to know... I know very little about my fathers family and past... always been curious, maybe something back there would explain a lot of what/who he is, but I'm a little scared of what I'd find.

really it is up to you, do what you think is best.