i prefer to put them in my incubator with 28°celsius
Too high of humidity will cause them to mold. Like I said my vermiculite is relatively dry. It's not moist enough to clump but you can feel moisture. That a very broad description sorry. I keep them in a sealed container, At room temp. They should do great the way your keeping them. If you want I can get a humidity reading At home.
I can't find anything on the exact humidity. I've never paid attention to that. Ive always kept them at 70.f slightly moist sub and sealed container. Look at this link. They have a great explanation on incubation and theres no indication on exact humidity: Crested Gecko Care Sheet
They don't need high incubation temps so high humidity isn't necessary the eggs won't dry out unless the sub is completely dry. Use a sealed container, your temps are great, and open the container every week. 90 days you'll have babies.
I found these weird she'll likes things in my tank there is a yellow powder like substance in one I didn't slit them I think they are eggs but these are my first geckos this is oneView attachment 44910