this is hoot n shoots prettier half here,
i have done quite a bit of bark tan
hickory is not on my list of high tannin content but that is not to say it would not work, trust your nose and taste the solution (w/o hide in it!) it should taste VERY astringent, leave your mouth feeling dry and puckery- oak,willow spruce,alder bark and sumac leaves are some other sources. walnut will not tan just great for dying.
as for your questions, i always leave the bark in and add fresh brew frequently for the first 10 days- for example-
hide in- stir several times at least every day for first few days
day three strengthen- stir 2-3 times
day 5 check solution- smells ok? and when hand is submerged cannot see my fingers 3-4" below surface? if no then strengthen
day 7 or 8 check again- the rate of absorbing has probably considerably slowed and my stirring is less frequent now - i may take it out and remembrane as you have done- more you stir the faster this will all happen.
depending on hide, temperature and the tannin content of your solution it will take a minimum of 2 weeks (that is absolute best case)- usually 3-5 is typical - a monster buck may take longer.
seems like your hide was DRY ("in your shed?") before going into the solution. may be fine for experimentation purposes BUT- i have tried several dried then bark tanned hides with not so great outcomes- the grain layer shrinks down tight and you must work the dickens out of it wet BEFORE putting it into any solution to prevent cracking of the grain. I say it is like trying to reconstitute a dried apple slice and getting to feel like a fresh apple- cells have collapsed before inserting the tannin.
hope this helps