I love the devotion here man!
I had done much the same in early versions of misunderstood needs for isolation and absorption.
What I found in the end is that most materials like you are using are also reflective. You may in essence be creating a smaller space than you have.
What mic are you using in there? What is the room size?
Is the cat's fur reflective or is it absorbing sad emotions? lol
I personally would recommend a dynamic mic, place some of those those absorption things like the mattresses in a 'v' orientation behind the mic as well as a couple other things behind the singer. Maybe the foam above. But that looks like closed cell foam so it likely doesn't do shit.
It is always best to stop poor reflections in a big room, than to create new ones in a smaller space. Well, from my experience anyway. Every room is different. Get rid of the 'boing' sound if the first order.
In my room I have a couple bass traps and some absorption panels on the walls (10 actually). But with a good dynamic mic, I realized singers could sit on the recliner on the side of the room, and still get a great vocal.
Not so easy with a condenser mic as they tend to pick up the room without caring about the proximity of the artist to the mic.