Did you consider applying for a Nexus Card?
I had one long before we got engaged and it helped me tremendously when I was crossing the border.
Not sure if they'll approve it but it may be worth a shot.
All I did was bring all my paperwork, a letter from my employer, bank account info and such.
I do have a full time job though that I've worked at for 11 years, so I'm sure that helped me out as well.
I never needed anything except the proof from my immigration paperwork.
Wish you the best of luck. I can't imagine how hard that must have been - to be denied entry
I would have been super upset if it were me.