Ammo is not a problem if you plan ahead. I doubt you would be shooting more than 20 rounds at a single sitting anyway especially from the SRH. I have a SRH in 480.
I noticed that Sportsman Warehouse has some Hornady 325 gr 480 Ruger and I have been buying a box a week. Building up the cache of factory ammo slowly as I don't shoot it weekly. I'm just about ready to sight in a red dot on my BFR. I'll do the 475 Linebaugh thing later after I'm comfortable with the gun.
Max Prasac's book is worth buying. You'll enjoy digging through it.
I think you are dismissing the gun and caliber too quickly. It would make an excellent PA whitetail gun.