Calumet really isn't downtown, it's over on Delaware ave in south philly. It's pretty hard to get to by public trans, and doesn't have good hours if you work a day job... Also, the last time I bought film there, it was dusty and nearing expiration. Meh.
Just outside of Philly east of the Ben Frankin Bridge in Merchantville, NJ is Dead Link Removed. They're one of the last REAL independent photo shops in the Philly area. That's where I go for all of my chems and supplies. They have pretty much everything, from 1L up to the big cubes. Their stock is fresh, and they're really nice guys. They've got a full rental darkroom as well.
I could probably order from Freestyle, but I much prefer using the expertise I can get at TDS.
As for your fixer question, I bet asking the guys at TDS would be a great way to figure out what you should do -- they've heard of EVERYTHING. Give 'em a call and then report back!
If you do end up going there, let me know. I like to show up with a 6-pack once in a while to share with the darkroom rental folks while we print.