Just looking at your Form and many of those fields are simply text, like names and addresses so they will be hard to validate.
Emails and Telephone numbers can be done using regex, but name, address and company names will be nearly impossible to validate.
If they are spam submissions, adding a captcha to the script might work to reduce some of the faulty submissions.
Or, another method is to add a "hidden" form field. If a Bot is filling out the form, they will complete the hidden input, but real people will not, so check to see if the hidden field is filled out and drop the form submission if it is completed.