By default google blogger blogspot uses these tags
Home page title
Post page title
for search engine ranking you should put one h1 tag in home page as blog title and one h1 in post page tag as post title because one h1 tag in a page is best for better search engines ranking.
Advice to use below tags for best SEO Practices
Change Home page title
Change Post page title
so you have to change only blog title and post title sidebar remain same as h2
link - change blogger blog title h1 to a tag in post page
link - change blogger post title h3 to h1 in post page
