Sarah's very existence proves that Aether and Nether can coexist - though figuring out how to master both will be difficult. Abyssal is, unfortunately, completely incompatible with anything else. Gods are jealous creatures.
For the time being, don't worry about screwing yourself - it's safe to learn magic and sleep with succubi/angels. Any major choices will be telegraphed!
I'm genuinely glad to hear that! I'm finishing up the upcoming mega-update now, should be out in a few days at worst.