CafePress doesn't really offer any "vintage" styled garments. All are 100% cotton (no cotton/poly blends that I know of).
They do offer some AmericanApparel styles (white shirts only)
Some will love the quality, some won't feel it's what they are looking for.
It seems you have some pretty specific standards, so my advice to you would be to create a design and upload it to a cafepress store and buy one or two of the products to see if it meets your needs before setting up a full store.
If you want to go the print on demand route, you may also want to check out spreadshirt, printfection and zazzle.
They do offer some AmericanApparel styles (white shirts only)
You can edit your design as much as you like before making your store go live. As for tweaking, you'd probably have to order your product (at a discount) to see exactly what it would look like as a finished product.
They use direct to garment printing and heat transfer printing. I have some cafepres shirts that look good after serveral washes, I have some (from their earlier years, that have faded quite a bit).
Some will love the quality, some won't feel it's what they are looking for.
It seems you have some pretty specific standards, so my advice to you would be to create a design and upload it to a cafepress store and buy one or two of the products to see if it meets your needs before setting up a full store.
If you want to go the print on demand route, you may also want to check out spreadshirt, printfection and zazzle.