No doubt there were some glowing character references of the man who left another blind & the woman who couldn't be bothered to walk her daughter to school.
I'd agree that João doesn't come across as everyone's dream son-in-law, but I haven't found any trace of the legal ruling in the assault case which landed him in jail, so I don't know what evidence his conviction was based on. Several members of the family said that he took drugs (but Leandro said that he believed he smoked hash / pot, not anything injectable). He had very little education and found it hard to find work, but his employer (past or contemporaneous?) said that he worked well and didn't have any problems with him.
Leandro stated that João was fond of his niece, but that he wouldn't have put it past him to have attempted to sell her, but didn't believe that he would have harmed her.
Regarding Leonor and the school issue, the only account of that (to double-check) is a written statement from the supermarket lady. Leandro and the rest of his family found that she paid unusual attention to Joana and wondered whether she could have taken her. That may, of course, simply be wishful thinking as it would seem to be the only potential "princess" scenario.