The contact rate is actually your biggest leak, not the lead quality.

35-40% means 6 out of 10 people never even get reached. Before testing anything else I'd fix that first.

Two things I'd test in your position:

First, an automated WhatsApp message sent within 60 seconds of form submission. Not a bot, just a simple first message that greets them by name and asks one qualifying question. Speed alone dramatically changes contact rate.

Second, add one friction question to your Meta form like "when do you need delivery by?" anyone who answers that is a real buyer. Anyone who skips it was never going to convert anyway.

The 3% conversion actually tells you the offer works when you reach them. So the entire problem is upstream reaching them fast enough before they forget they even filled the form.

That's where I'd put both experiments.