Is it normal that you have to add a lot of salts to reproduce burton water? yes.
The problem with putting all of that into the mash, which I'm guessing was your plan, is that if you had actual Burton water a bunch of stuff would drop out in the HLT. So adding the salts to your mash that would have produced burton water had you added them to the liquor is not the same thing at all as brewing with burton water.
That said, they don't make rye pale ale with american hops in burton, so I don't see the point in using burton water anyway.
Personally I would add gypsum to get a sulfate level you are happy with and leave it at that. The vast majority of hoppy american beers are made with sulfate levels much lower than burton.