Security Staff in MAD are contractors from a private company and is a really low-paid work so don't expect any proficiency in languages. Young policeman/women are supposed to pass an english test and usually they know some from high school / university but old ones basically are not required to know any english at all.

And yes, they are really keen on following the procedures (especially because they have 'quality supervisors' looking at them) about liquids and staff. Every time I come back to visit my family and friends I bought an insane amount of pork food to bring back to my home and they always want to look at it. Not touch it or examine it, just look it.

I can't find anything in the AENA guidelines about checkpoints but I'm pretty sure you can actually leave to check-in stuff (last time I was in MAD T2 checking-in a girl was checking-in an oversized bottle of perfume apparently after being rejected in the checkpoint) but the language barrier may be a problem