I bolded and numbered your questions to make it easier to answer.
1. Yes, it will be a problem unless the desk clerk that checks you in and out is really not sharp. Consider Virtuoso as a way to solve this problem as there is no membership requirement
2. yes you can book more than one room under FHR for a single stay
3. I believe at the Wynn it is a fixed credit for breakfast. Doesn't matter if you are one or two people. They won't be flexible
4. Yes... but you have to check out and check back in again. Makes your problem in question 1 even harder
5. Sorry, no idea.
Well. I thought I should follow up in case anyone else has this question in the future. I called both Amex FHR and Wynn and BOTH were adamant about the cardholder being there with the Platinum card at check in. I honestly didn't want to deal with the risk of them giving me a hard time, so I canceled it.
But I went over to visasignaturehotels.com and booked the same exact thing as FHR with only one difference. Price was the same; free b-fast, free upgrade; 3pm "if available" checkout (granted, not guaranteed but I didn't need that anyway); instead of $100 spa credit, we got $25 dining credit.
I've had that visa sig for 10 years and never even knew about the hotel benefit. Grrrr.