I opened a new online store?

[Jake]

Perhaps it's your being far north that explains your representing the postal service as USPC, which seems to actually stand for "United States Pony Clubs, Inc."

USPS stands for United States Postal Service

Having only an email link for the contact us page is kind of bush league, you should invest in a tole free phone number service they are not too expensive (more professional companies manage to deal with telemarketers), some have multi-department voicemail navigation that makes you look big time.

Your address is already given up in the Upfront Merchant window, may as well add it to a Contact Us page as a mailing address to boost credibility, along with the tole free number and a contact email form.

The payment description on the about us page seems a bit complicated

Perhaps something like:
Credit card payments securely processed by paypal, no account needed.
Paypal Logo

(paypal members will know what to do with their account)

Adding some vaguely related articles will help you get more search engine traffic, either in an information tab or an added blog, your FAQ while thorough, doesn't have any pet specific answers like how to select a size.

You could probably have a bred to size chart to simply fitting.

It takes money to make money, if you can find paid advertising that is even close to reaching break sales conversions, some sales funnel optimization might turn such traffic into a scalable source of profits.
Read up on split testing, Google Webmaster tools have a free service that compares effectiveness of 2 design variations. Optimization of the sales page conversion rates is a big deal, big players will lose money sending lots of paid ad traffic just so they an get quicker test results leading to an optimal design.

These guys have studied a bunch of design variations. http://43splittests.org/