Well, its really hard to answer such a question without you having had written anything.

Okay, here is what you do.
Go get a concrete chisel.

A big 4" and break all the mortar off the stuff on the floor.
You set the chisel next to the vertical step and bash down.

I didn't see what wire you put into this first coat of mud.
If you used something heavy gauge, then reply and i will tell a better way.

So, you break off all the concrete on the floor.

Then roll the carpet out of the way of the new, larger, floor area.
Leave the carpet rolled. It creates a berm that corrals kids.

Get the stones you are going to use on the floor. Lay them out.
Chisel them where needed.
Outline them in pencil, then put down some concrete board over that area.
Then, instead of laying down a scratch coat, just lay down a good bed of mortar and set your stones in it.
You would like a good 1½" of concrete with some fine reinforcement. 10/10 or smaller.
Ladder reinforcement, like for brick walls, works well.

Your problem is that you are in a trailer.
It bends, all over the place
It expands when hot, and shinks when cool
You need a floating concrete beam that will just sit on top of it.
You aren't going to build this in two coats.
You want to do it in one.

Finish the upper area just as you have planned.
These two pieces aren't really going to be structurally connected.
And even if you try, it will crack at the point i told you to chisel things apart.
So, you just deal with that. the cracks will be at the backs of the stones.
You try to hide this in how you construct one over the other.

Now, if you really have a problem where you cannot take the concrete apart, then you just use epoxy.
There is epoxy for concrete. You mix it up, spread it on (thin) and then place the new concrete to cure on top of it.

Again, you really want that 1½" + concrete slab to just hold itself together.
You don't need coats to build it up. You do not need it firmly attached to the trailer.
You want it all stuck to itself.

After you get your stones done and they have cured for a couple days
then put down your tack strip, replace the padding and pull the carpet tight to the stones.

And, the last piece of advice.
Take a deep breath. It happens. Kids happen.
AND! you are going to begin construction of real house next spring.
Your bitcoin you got is going to be way more than the cost of building a house.
In fact, you may have enough to retire, and just build house and raise kids.

Oh, let out the breath. Don't stop breathing. :-p