1. NO! I've rented many a cargo van and found that basically no consumer card covers cargo vans (or pickups for that matter). The only exception is the American Express premium rental car protection that you can add to basically any Amex card for a per rental fee (not per day) of about $20-$25. I've read over the plan documents and called several agents from the underwriter and all have confirmed that cargo vans from a regular car rental company are covered. No cargo box trucks, and nothing from rental moving companies (I assume U-haul, Penske, etc.). YMMV, read over your contract/coverage documents, IANAL, etc.
2. I'm not sure, but Notwithstanding point 1, I've rented vans at airport locations for the same reason (cargo van significantly cheaper than anything else). They would call me the day before to tell me they were out of cargo vans and if a substitute was ok. Even if they had the van, I figure worst case as a PC I could kindly request a downgrade. In all cases though, I would have been ok with a cargo van. FWIW, the ford transit is the best cargo van in terms of equipment and ride quality compared to anything else in the class. The only mainstream one I've not tried is a Sprinter frame which Hertz doesn't seem to stock.

One thing I would recommend is call them to see if they expect to have a cargo van. My usual HLE will often stop at nothing to source a cargo van if they don't have one and I hold a reservation. In fact, they've gone as far as one state over 2 hours away to get one. So in your case, maybe you can help both sides out and have it noted on your reservation that you don't actually need one in case they would go out of their way or if they had more reservations than vans.

Hope this helps! Good luck