Is the snake male or female? If it's a male, that enclosure will likely work fine.
If female, she'll almost definitely outgrow it, and probably sooner than later.
Another thing , is it possible to feed him just mice pinkies ( like 3 at times)?
Yes, you could, but pinkies are primarily water, so they get next to no nutrition from them. You're better off feeding one appropriately sized prey item. At that size your boy can easily take large hoppers.
Another thing , is it possible to feed him just mice pinkies ( like 3 at times)?
Not recommended no matter what the amount is and it would take more than 3 pinkies for a 2 feet snake.
Pinkies are just a blob of water and fat, no hair which binds and most importantly no bones which provide calcium, pinkies are what I feed hatchling that are a few grams.