Phenji ,
One chardiyan kalan phenji once told me this.
In matters of marriage , everything cant be foretold or measured in advance.
SO , the only way is to do daily ardas " asking guru ji to give us such a gurskh jevan-sathi , ki jag vich aaya safal ho jaye" and do an extra Japji Sahibs path in this context.
Then guru Ji takes care hiomself , even if life partenr you choose may have bad intentins or nature in the beging ... guru ji takes care and changes him/her...
I think in your situation , do whatever information gathering u can do. But then stop as there is no end to "chinta" etc.
Do ardas and make sikhi your parameter of measure and if you feel right go for it. :TH: