Look into a 212(d)(3) waiver, which should allow you an entry. Ask CBP at the border how much time they need to process the waiver (usually a few weeks).
You must tell the truth. The better visa for you is K-1, if you want to get married in USA. Your chances of getting a B visa do not appear to be very good.
He can be denied entry. UK citizens have the same options to work in USA as the rest of the world; typically H-1, L-1, E-1 and E-2 visas.
You can go to a third country, but your entry back into USA can be declined if CBP believes you are spending more time in USA than you should. Typically, B visas are for brief visits (may be six months or less in a 12-24 month period).
You will need an unexpired passport to enter USA. People in your situation carry both the new and the old passports.
Tourist visa seems to be appropriate. Times vary by consulate and are usually very short -- often visa is issued the same day an application is made. You can also get an appointment for emergent reasons.
She will be at the mercy of CBP at the airport. They can decline entry.
You can file I-130 and I-485, but she must not travel outside USA until she gets her green card.