Pawing and being mouthy are all typical traits of mastiffs. Mastiffs need to be always in constant contact physically with their people. It takes a while to get the message across, but if every single time he puts his paw on you, you turn around and walk away from him immediately- no eye contact, no talking, yelling, etc. and totally ignore him for a minute or two EVERY SINGLE TIME he will eventually get the message that putting his paw on you is not allowed. "Talking back" isn't really what it seems to be. Mastiffs are very vocal, and you can actually use it to your advantage. When he barks or "roo"s at you, tell him "good speak" and give him attention or a treat, which will eventually teach him to speak on command, is the first step in teaching him when NOT to bark at you. He has to know the "speak" behavior before you can teach him not to do it. I can give you the info on training him to "hush" on command once you have taught him to "speak" on command, if you need it. I have four of these monsterous guys in my home right now, and every one has been taught not to put their paw on me ever, for any reason. They all also know how to "speak" and "whisper" on command.