To expand on what @Laura_S said for #1 Part B only covers insulin for pumps purchased with Part B. The only ways to get no cost insulin is with a Part B supplement plan or one of the Medicare low income assistance programs.
#3 and #4 Omnipod has a bolus calculator or you can figure out boluses same as you do for MDI. For more info on how the Omnipod works see Laura’s recent tips topic Omnipod 5 Tips - #2 by spdif
#5 I’m not on medicare (yet) but I did a quick search with my zip code and like you none of the plans covered Fiasp. Wild guess but maybe its because Fiasp was on the list of negotiated drug prices? Lumijev is covered by a couple of plans with $100+ monthly premiums. And I hate suggesting changing medications because of insurance.
*When you do your how long to reach the price cap math don’t forget after the first 3 or 6 months your endo is going to change your Omnipod script and do the paperwork to get you one every 2.5 or 2 days so you have spares on hand.