Since you have access to Farfard products, look for their Professional Potting mix. Not exactly the same as the gritty mix but one of the closest (and better quality) commercial potting mixes available. And no added ferts - you can keep with the Foliage Pro.

i'd suggest going a little bigger, not too much, since you're in a cooler climate and will be moving it indoors. probably around a 14" wide X 12" tall pot would work well. if your tree was rooted it may be a full sized variety, or if it was grafted most likely onto a dwarf rootstock and it would do well in a pot. do you know if it's grafted? i dont see a graft line in the picture. and it seems to be planted a little deep. remove some of that debris away from the base of the trunk, and a little of the soil and take another pic.

A large 5-gallon bucket with water like Mike said works best for me. Let it sit in there for a while, and then slowly swirl it around until soil falls away. You want to keep as many of the fragile roots as possible.

Michael, I understand your frustration as I have been there done that many times. I suggest your using a 14" wide pot if you want your plant to get the best growth ASAP. I typically get mine at Walmart and get the cheapy plain type that comes with a drip pan attached. They are about $10-12 and you will need the bottom to protect your floors in the winter. They do carry the more decorative fake terra cotta as well which is pretty. A 14" pot is definitely too wide, but your alternative is to manipulate the roots to fit into something smaller which may shock the roots for a short time. I did that with 3 trees that were in the same sized sleeves as yours almost a month ago and they are just showing new growth. I didn't want to spend a lot of money on pots so I went to the Dollar Tree and got cleaning buckets ($1 each) that were equal to 3 gallon pots. Yep, I am cheap and would not have any use for the pots after this batch so why spend a lot of money? The other 2 trees (same sized sleeves) I had were planted into 14" pots, with minimum manipulation of the roots, adapted much faster into the new soil and put out new growth within 2 weeks. I suggest your using a potting medium that has a lot of bark and perlite when using a 14" pot or 5 gallon bucket. To avoid trees that come in a 4x4x13" sleeve, buy older and larger trees. Those typically come in 3 gallon containers and you'll get fruit sooner too.