Yay, you're going to Disneyland! Woohoo!
As for your questions:
1. Before check in at 3, where do we park? Are we allowed to park there or do we have to buy parking at the garage?
3. Do all rooms have a view of at least a parking lot?
4. Is there a way to upgrade your hotel and not spend all 5 nights downstairs but get to go up top for a theme park view for 1 or 2 nights?
5. Is there free breakfast?
6. Is there a resort fee of $16?
10. Is there an entrance into DCA? I could have sworn I read that about PP, not just GCH.
For all 6 of these questions, I would call the hotel. They will be able to provide you with the most accurate and recent information and would very easily (and quickly) answer each of these questions.
2. Our package will include a Toon Town ticket. We won't be using it, and I read that people sell them on Ebay, so I could just do this?
I have never had a ToonTown ticket nor sold anything on ebay, but you can sell just about anything on ebay, so I am sure you could. (Or you could give it away to someone on DIS who is wanting one.)
7. The Costco package comes with "Premium Character Dining." How much does this include? I can go to either Ariel's Grotto or Goofy's Kitchen, but is it just once?
The paperwork or offer should say what it includes. Is there a phone number? Since we don't know specifically what package you bought, this is a difficult question for people here to answer.
8. Is there a way I can say we are celebrating our anniversary and get something a little extra?
You can let the hotel know that it is your anniversary. They can note it in your reservation. You may or may not get freebies, but you will allmost certainly get anniversary wishes.
Here's to an exciting trip,
Dreams
P.S. Just for my own confusion, you mention anniversary, but also DBF. Do you mean husband?