May I send a file with multiple pages sized 5X7" for printing on cardstock? If so, how do I correctly send them to you?

To get the best answer to this specific question, please fill out our PRINT QUOTE Form

Hello ! How much to print 80 pd cardstock ? Color two sided ?

Through this product, you can check the pricing of what you are needing.  There is an option for 80 lb card stock in the listing.
https://www.cutcardstock.com/collections/templates/products/discount-cardstock-add-printing

I'm trying to find out how much it will cost to buy 100 recycled paper envelopes and print the return address and recipient address on them. I want pricing for printing both on the front or recipient on the front and return address on the back. Is one envelope considered to be one sheet?

It will be most cost effective to do the return address on the front along with the recipient.  We can do the recipients and this would be best done by reaching out to our customer service-printing department and requesting a quote.  Or you can put an order in with the envelopes that you want and then adding the printing costs to the order and adding a note to the order that you are also wanting the recipients on the envelopes.  Our printing department will reach out to you via phone or email on the files that they need from you.  The envelopes are priced per sheet and getting the print on one side rather than 2 sides is the most economical.  If both sides are black ink, it should not be that expensive. 

I want to send semi-customized A7 cards with name/address altered and inserted from a merge file. Is this type of print service offered?

Yes, this is something that we can do, please contact our customer service at 219-764-2070 or admin@cutcardstock.com for help on placing this type of order.