I can confirm on my current tune by X i was putting in 4.6gal of e85 & the rest shell or chevron of 91 gas. Every fill up I also put in 25mL of AR600 Archoil. Never had a slip on my DCT. It was just a hassle to do these 3 things when filling up sometimes.Up to you if $ for upgraded shocks will be worth it or not.
I'd keep the oem pump and line until you have issues or need them. Unless going to run higher E fuel then I'd upgrade both the pump and the line. I say this with some hesitancy as I'm not sure if the DCT will slip before the fuel demand of E85 will overcome the need of a pump and line or not. So I only say this to be better safe than sorry.
This time around i wanna avoid such hassle & from what your saying that simply utilizing 91 only will be best for safe power?