Hey Kit! Nice work! You should look into putting an AddThis bar below the comics. They've got a tutorial specifically for Blogger that makes it easier here. On Blogger, I'd go with "On Each Blog Post", because I think a lot of folks might use the sidebar links without realizing that those will go to the blog's home page instead of an individual entry, which is what they probably want to share.
In a big random coincidence, I just found this comic on your birthday by looking through your sister's DA and finding a birthday picture she drew for you in 2010 and following the link in the description. Happy Birthday!