I'd love to help you with your Google Ads in any way you need. I am a founding member of the world's greatest Google Ads Mastermind Group - YouVsGoogle. I've managed Google Ads, Google Analytics, and Tag Manager for the last 12 years. If I can't figure it out your problem - my professional colleagues will have ideas. Access to the best of the best is what I offer.
While I am heavily involved in account creation and management, I have skills strategically that only come from long hours being involved in more than 500 Google Ads accounts and making a conscious and recurring effort to talk shop with other experts. If you give me the time and follow my instructions and that usually involves a commitment from you to invest in creative as well as scrupulous attention to adapting your site - all of the accounts I get a hold of do get better. Ultimately you have to do two things to succeed with Google Ads - (1) Do it the way Google Wants. (2) Do things that are additive and different than your competitors. These are the keys to Google Ads success.
You might get reasonably current, but accurate is much more difficult because of all the contributing factors that go into it. That said, you can start with what you have access to already. If you know that your offers in a sphere are taken by 20% of the people who elect to view them, that can be a starting point. If you visit trade shows and you ask enough people you can get a sense of conversion rates online. They vary a lot based on the the reasons (and search terms, or prompting) why users choose to a view an offer. Once you get a rougfh estimate of the conversion rate, visit adwords or get a temporrary sign up at semrush or spyfu and enter a seed keyword for your industry segment and find out the average cost/click. - do the math - 20 bucks/click on a 20% conversion rate would be a $100 CPA