Dress Question

You're right that the shoes are only important when it's time for alterations. I brought a nude bra and nude underwear, but I didn't end up needing the bra, as all the dresses I tried had inbuilt support. I recommend clothes that are easy to take on and off if you're going to several stores, as loads of buttons or snaps or whatever gets old very fast and putting the dresses on and off alone is tiring.

if you know there is a type of shapewear you'd really like to wear on your wedding day, you might find it helpful to wear it so you can make sure it's covered by the dress you pick, but that is only if you're deadset on a particular style or brand. Otherwise, just relax and have fun

I say your FH is spot on (good on him!)
Wear heels in a height that is comfortable to you. It does help to have an idea of what you will look like in heels because (let's face it), certain parts are accentuated while in heels, and he's the one looking.