Will search engines be able to read the content and index my site? Will it hurt my SEO?
It would hurt usability - sometimes people may want to copy text or simply right click for very legitimate reasons. Now. usability is a factor for SEO but is this particular thing an issue? Likely not, but one can never know.
It does give you a little piece of mind that you tried to protect your copyright and it does give those who manually copy text for reposting a sort of warning that you're serious about it, but that's about all.
I would say only do it if there are few people who steal your content constantly and you know that they are much too stupid to figure out the workaraunds.