I agree with Maximo. Are you open to brush recommendations? We love love love our Madan brush. I loved it so much, I stole it from my pup and use it for myself. I bought it when I was attempting to grow out his coat. A long soft coat is not a good idea! My pup was tangled and miserable the entire time. He's kept short now, and I use the Insinis boar brush on his hair, and the Madan mustache comb.
Don't worry about the hair growth. It will come back, and will probably be better than his puppy coat.
As far as clothes go, clothes help create matts. If you're going to dress him often, a shorter coat is best. If you're going to dress him while his hair grows out, just remember to brush the chest and under the front legs. That's where I found most of the matts on my little one. You can find clothes anywhere really. Lots of good YT vendors, Target, Petsmart, Petco, Ross, old navy use to have nice clothes, you can make baby onesies into clothes, and there are lots more options.