I have already reported to the police and FBI. I'm looking for a private investigator now.

Just to find out any additional information. I'm well aware recovery of funds is all but impossible, but I would like to know who was involved in the theft. Even if I cant find out who specifically I think the right person could likely uncover more than I know now.

I am unsure if the FBI will take the theft of $40,000 seriously, and the local police are often unequipped to handle this type of case. Perhaps if this hacker has stolen significant amounts from other people, he or she will be investigated. I'd investigate this through the blockchain, though that's not likely to be fruitful. Also, with that amount in cryptocurrency, it's a reminder to invest $60 for a hardware wallet.

All you're likely to get is scammed again.

It’s only through a very good private investigator who specialized in recovering money and scam cases that can do this. I got scammed through a dating site, looked for different ways to get back my money both online, contacted most private investigators through their website online only to find out they weren’t specialized in recovering money until I came across ‘Adrian Gonzalez’ on quora. I had to sign up to view his profile and contacted him about my case. He is the only one who was able to recover my money, others I contacted couldn’t at all. I will advise anyone who has same issue with me to reach out to him for help. I wouldn’t want to call out the names of the ones I reached out to and wasn’t able to do nothing. Adrian Gonzalez is the best for recovering scammed money.

They will first need a system that can do it. Somewhat like a bad hacker vs a good hacker idea. Their should be a solution to a problem created by that software and system. It's an online thing that are too wide to be analyzed and identify.

Hmmm.
So it's New Years Day, and Jessica here decides to register on a Bitcoin forum, necro this thread and tell us how good "Adrian Gonzalez" is at recovering money (supposedly lost on a dating site, so probably not crypto anyway).
Hmmm.
There is indeed such an entity as him posting, seemingly soberly, on Quora and boasting a CV full of buzzwords.
As most people get ripped off in the first place by NOT doing their due diligence maybe now would be the time to start doing it, starting with Mr. Gonzalez impressive list of qualifications.
NEVER give anyone money upfront is a good credo.

You are likely going to spend huge sums of money on that. Why don't you move on and rather save the extra money on how to protect yourself and also get yourself some hardware wallets to use. I believe this is much important than trying to go on this wild goose chase which is likely going to yield no results.