Sending healing rayz for Theo. Kasianni, you are in the best place for info and encouragement. The wonderful folks here at DLC kept me sane when Frankie had back issues.
I used the same crate for him that you have (the black one) and it was perfect. A very smart person here suggested tying it down on a movers dolly which was great since I could move him around from room to room with me. I used a pet stroller in the beginning to move him around with me but as he started feeling better he wanted it jump out of it which scared me. So, the crate on the dolly was my constant companion which made Frankie happy and a lot calmer.
Hope your sweet boy is better in no time!