On LastPass, it may be filling in the hidden spam field, or you may have the options to require mouse and/or keyboard use turned on, since LastPass won’t be using those.
On the path problem, it’s unlikely that it’s SPForm. I’d look at the template for the pages with a link to the contact page to make sure the href in the link is correct. Also, the base href tag in those templates, should be
<base href="[[!++site_url]]" />