It is essential to an extensive A/B testing first. Otherwise how can you possibly know that 11px is better than 10px?
I'm all for A/B testing, but the problems here are at a much more fundamental level--it is about understanding your market, and matching your customer's expectations. There will be plenty of time for A/B testing, once the sales volume is there to support it.
I'd also agree with @patio11 - the website is outdated, unprofessional and I wouldn't trust it. I'd pay a decent web designer a couple of thousand to get a bespoke design that will be much more suitable than what you have now.