Well done!!!!!
Choosing investments vs mortgage debt is a personal decision, generally, the maths works out better with investing (IDK about the tax in the US). If you have a really strong desire to be debt free (and this is not just because Dave Ramsey says so), then paying off the mortgage is probably right for you. To me then having more savings than mortgage is the same as being debt free, but I see that this is different for other people.
As you are looking to be FI at 45, think about how much tax advantage you can get in the next 14 years (14*$18k = $252k ?) and how this compares to your FI number. I found that I needed to get all the higher rate tax advantage I could, which meant it needed to start early. Would there be a benefit to putting all the pay that would incur 25% or 28% tax into the retirement account and the rest onto the mortgage?