Moving to a country where crypto gains are not taxed is a very good idea in such a situation like this, but before you choose doing this as your final decision, you have to sit down, take a piece of paper and a pen, and maybe a calculator  and calculate how moving to a new country will cost you, not just your flight ticket and other logistics expenses but also how much it will cost you to settle down comfortably in your new found country..

Then, calculate how much money you are going to pay as tax in your country if you decide to stay there and convert the BTC2.5 to fiat as it pleases you..

Which ever comes out lesser I think is the best option to go for here, I don't live in France and don't know or have idea on how the country have programed their system to take note and accurately calculate profit made from crypto but here in my country, there is no such thing as crypto tax, maybe get a good lawyer, he or she will be in the best position to tell what's best for you to do.