Which size SKS Bluemels will fit my frame - 35, 42, 45?
Choosing a maximum size for a given frame is not an exact science. It's done by either mounting or approximating the widest size tires you want to be able to run and then using a caliper or ruler to see what you've got to work with in terms of vertical and side to side clearance.
Your bike looks like it shouldn't have trouble with the 45mm. That's probably the number to choose, unless by some chance there's clearance for 50s.
Two things people often under-consider in the abstract:

7mm total overhang in width gets thrown around as a bare minimum, and you can see SKS follows this line, but it's really pushing it in practice. In addition to being barely adequate for spray, it makes preventing rub finicky in day to day use. How easy they are to live with is actually one of the bigger factors in choosing a width. A 28 in a 45 does not look funny or perform badly. It's actually great.
Wider means more wrap means the tire can be more sunk in means wider may function where narrower won't even if it's not needed for coverage, if vertical clearance is limited.