I'm afraid FindMy will not be incorrect. Yes, it can get stuck in a previous location, but that is not what the OP is saying here. Not only is it showing a location in Benalmadena at the current time, it's showing him moving around along streets and between distinct premises. That's where his phone is, and for now the working assumption is, he's with his phone. I'm sorry OP.
Whatever you do, do not confront him before he's home and you've gone through his phone - the tactic described above of going to the loo is a good one. If he gets the chance to delete evidence it will drive you crazy going forwards. You need to know what's going on.
For those saying why lie about unimportant things, it's what dishonest people do. They over embroider the truth, as if to say, " Look at me and how honest I'm being. I'm telling you more than you asked so I couldn't possibly be lying". It's a thing detectives look out for and it's a sign of a guilty conscience.
In this case, drawing attention to "Faro" airport catches my attention.
It's also always possible of course if he tells the truth that OP might say, "Ooh, I heard yesterday x and y are in Benalmadena this week. (Mentions hotel next door to his). Which hotel is you're in again?". If he lies, he won't run the risk, however slim, of having people he knows looking out for him.
I'm sorry you're going through this OP, try to stay calm and focused and get your ducks in a row. Tears and anger can come later if required. Good luck. x