The man after them has managed to find whereabouts they are now as the boy put his real name, rather than the "safe house" one on his sailing application form, so as the sailing instructor took photos and uploaded them with the boy's real name.
The sailing photo then came up when the man after them was searching for the boy's name and would have been linked to the sailing place, which is right near where the safe house is, and the sailing instructors will know where the family are, and as they do not know they are in a safe house, would not have any reason not to let it out.
The boy had realised he put his real name down by mistake and told his mum (or not, as it turns out) who didn't seem to realise the potential seriousness of what had happened and the risk of them being found.
The bloke in prison is, I think, the husband of the lady the policeman was trying to look after when they got shot, who she was testifying against. He has obviously found out it looks like he was more than just protecting her (with the kiss CCTV) and is not after him.
I'm wondering if the policeman investigating had some hand in the shooting (giving information to the hard man in prison or something) which is why he is trying to stay so on top of things.
I'm sticking with it, isn't it the last one this week?