Keyword spamming means you are using repeated keywords in the content, I mean to say that high keyword density can cause keyword spamming. One more reason for keyword spamming is that you are using your keywords repeatedly in title and description tag for the website.

Dear You can use only one H1 tag for a single page because a page can only have single main heading. After using H1 one time you can use sub heading tags like h2,h3,h4,h5,h6. Serach engine puts more emphasis on the content mentioned in heading tags.