Regarding each of your points:
1) Which ones are problematic theologically? All of them, or a couple? And if you have grammatical problems fix them. The Ibn Ezra is usually not accepted as a major Halachic authority, despite his value as a Parshan. And where is this Ibn Ezra, anyway?
2) The Sfardim don’t say Piyuttim because of Hefsek. If you’re going to follow them, go all the way- don’t say the popular, responsive piyyutim either. If piyyutim are muttar, just recall that this is your time to daven for yourself and the tzibbur for the year- an extra hour won’t kill anyone. If piyyutim are muttar, they should be said. In any case, I highly recommend you say the Hin’ni, with a lot of Kavanah.
3)So switch. But if you’re going to disregard minhagim in favor of older ideas and follow Rav Soloveitchik, you should also say Slichos on Yom Kippur, like the Minhag Hag’onim. (If you’re worried about Hefsek, say them afterwards, I guess.)
4) If I recall correctly, we skip from M’sod to Zochrainu on the second day of R”H Mussaf.
In conclusion, I find your desire to pick and choose whatever strikes your fancy troubling. Pick a Shitta and stick to it, no matter how uncomfortable it makes you. Don’t hide behind whichever posek you like at the moment. “Oseh M’Kulai Bais Shamai U’M’Kulai Bais Hillel Rasha” (R”H 14b)