I think Jack was local, street smart, confident in his manor,knowing the area inside out and the police beats and possibly stalking victims by observing them in local pubs, he may have observe Kelly in the pub when she returned to prostitution after Joe left. Profilers have placed him as living in the Flower and Dean street vicinity. An average ordinary workman.
He made no sound which suggests instead of heavy hobnail boots he wore soft soled shoes.
One of the professions I have put foward for him is an offal dresser. They can removed the offal from an animal is less than a minute. It requires certain knife skills, is monotonous work and desensitises blood and guts.
The victims had to survive in appalling conditions, they managed to get by, have relationships, get drunk sometimes, have rows. They were no more or less vunerable than anyone else in the East End,probably better off than women who were regularly beaten by their partners or husbands. Life in the East End was dangerous for all women.
Bingo. and I like your suggestion of an offal dresser.
__________________ "Is all that we see or seem
but a dream within a dream?"
-Edgar Allan Poe
"...the man and the peaked cap he is said to have worn
quite tallies with the descriptions I got of him."
-Frederick G. Abberline