0.05% is high to start with. I'd keep it simple and buffer it at first either by mixing it with moisturiser or applying it after. Start 1 or 2 times a week and slowly builld up to 3x a week.
Niacinamide alongside it is good but IMO 15% is excessive, over 5% it potentially becomes irritating and drying, which you'd already be dealing with from Tret. It's niacinamide and ceramides that you want as support ingredients. Niacinamide soothe but ceramides helps restore. Are you normally oily/combo or dry?
Yes, keep it simple in the morning and don't use any other actives (like Vitamin C or acids) while you're introducing Tret, you'll have to reintroduce those later, again gradually. Cleanse (if you're very dry skip cleanser and stick to just lukewarm water) moisturiser and then sunscreen. You may want to switch sunscreens to something slightly richer with healing ingredients like centella, anything labeled CICA basically, Bioderma does a good one. You may find chemical sunscreens to irritating and have to switch to mineral only.
At night I'm very basic with Tret, I just apply it on dry skin after cleansing, just mind the amount. A pea size (and less than that when you're starting) really isn't a lot. I find it's overuse of product that often leads to the excess peeling as we're so used to liberally applying product.
For the rest, make sure the other products in your routine are without irritants, so no fragrance, essential oils, etc.