Give posters a reminder and chance to edit posts (ive seen lots of rule 3 violations on otherwise decent posts)?

I try to do that, the only time I personally do not give someone a chance to either fix it or delete it themselves is when they are spamming.

Rule 3 is very important, and there is room for some 'speculation' as long as your post it as a discussion with a linked source in it and an explanation as to how you believe something is related/important to pizzagate. If you do those things, which are simple, then your post will not be deleted unless it violates some other rule.

Or delete and encourage resubmission?

I know many mods do this, I personally do it (sometimes I even message the user and tell them that I would upvote the submission if it were on v/conspiracy instead of here)