DogBoy

I have a 2018 roubaix di2 with an ultegra R8000 50/34 crank. I'd like to go to a 46/30 crank to get my cadence right on some of the really steep hills around here (15% grade) I already have a 36 on the cassette, and I can't handle a larger cassette without changing my groupset, which is even more $$$ than I'm already contemplating. I'm pretty sure the SUGINO OX2-901D Compact Plus+ Crankset has an IDS24 spindle which I think works with my bottom bracket (hollowtech II), but I'm unsure if my front derailleur (ultegra DI2) can handle it, and I'm unsure how to establish that my chainline is compatible. I don't want to shell out almost $400 on an experiment, so I'm curious if this is something that will work? Mostly I'm looking to know what specs to review to make sure it will work, not asking someone to do all the work for me. I've been just riding my bikes without messing with them for like 10 years, so I've forgotten everything, and then everything changed as well, so I'm back to ignorance.

My cycling is long and slow, so I don't need the higher speeds that the 50 provides, and I'd rather mess with as few components as possible.