How should I go about validating an idea using interviews and surveys?

I lean on the interview method for every idea I'm serious about and it's never failed me. If your website has a lot of traffic your approach could work, but in my experience it's usually on me to hunt for interviews. If that turns out to be the case for you despite your web form then you are not alone.

It sounds like your target is other businesses. When I'm targeting a professional audience I try to find the most junior employee at the smallest possible company that still fits my target market. This means the company would be the right size to need/want my product and the employee is at just senior enough of a level to influence the decision.

The reason behind that approach is not necessarily scientific, it's just based on my experience getting people to reply/engage. You can think about the reverse logic to understand why it makes sense - accessing the CEO of a large company is likely the hardest path to validation interviews.

In terms of content, I focus on questions that help me understand the current things the company is doing that are relevant to the problem I'm solving. You want to know as much as possible about what problems they're currently facing and what they're currently doing to either cause or eliminate the problem. I try not to focus them only on the problem I'm trying to solve, because sometimes you discover a bigger problem they're having that's adjacent to what you were thinking about.

Your questions should be about facts or absolutes and less about sentiment as much as possible.

Good:
"Do you currently send drip emails to customers that abandon their cart?"

Better:
"What do you do when a customer abandons their shopping cart?"

Not as good:
"Do you think you would use a drip email service to convert lost customers?"

This is what's worked for me, but I'm also always learning how to improve at it. Good luck and definitely post more questions if you're stuck.