It's certainly possible! Fox is just tan + the chinchilla gene. Breed your fox to a black tan and hey presto - tans! If you don't have a tan available breed your fox to a self, but make sure it doesn't carry or display the chinchilla gene. This mating will give you tans carrying chinchilla as tan is dominant and chinchilla is recessive.
Yep, but nothing with the c-locus like siamese, cream, PEW, etc or you'll end up with some bizarre c-locus varieties with white bellies. Black, blue, dove, champagne, those kinds of colours will produce tans first time.
I bred a black carrying dove to a dove and I should have had roughly 50% black and 50% dove in the litter, and I ended up with 9 dove bucks and 1 black doe! Each kitten would have had a 50% chance of being black or dove just as they have a 50% chance of being male or female, it just so happened that 90% of them were dove males. Your fox must have one tan gene and one self gene, and by sheer randomness none were born with the tan gene.