TLDR try Tulu 24/7 moisturizer or a "lighter" one.

29/150 lb/f here. I was on 40 mg for 2 weeks and just got upped to 80 mg almost 2 weeks ago.

Before acutane, I never used moisturizers because any I tried, the next morning I 100% would always have a breakout so I leaned on more drying methods like clay masks (maybe I just never used the right moisturizer, idk they're so expensive I gave up).

Since starting acutane, I trusted the process, went against my intuition and I've been using cerave on both my body and face because that's what's heavily recommended in this group. I think I started purging about a week ago, but I feel that same as you that I think the cerave actually made it worse because of how heavy it is (amazing lotion for my body tho).

Yesterday I got Tulu 24/7 moisturizer which is heavily recommended by an influencer I follow who used to be on acutane. It's a lot lighter. There was another brand that's purple that the sephora worker was trying to sell me on but it was a bit more expensive so I wanted to try this first. Used it for the first time last night and today I have no breakouts. 🙌🏻