Never mind the first two questions. Try this:
Up top in the main toolbar, find your User ID and click on it. That should take you to your Account page. Over in the right hand column, click on Account Upgrade. On the next screen, click on the $25 choice. That should after a few seconds take you to a PayPal log in page. The email address that you use for Hobby-Machinist should be pre-filled on the PayPal log in window. If you use the same email address on PayPal, enter your PayPal password and proceed. After successfully completing the transaction, you should be returned to H-M.
I'll report the problems with Donations.