Yes to both. Area Damage is literally the only paragon stats that does anything for M6 in its category. Thats why most have Area damage and gold find.
IAS increase your attack speed and your attack speed combined with TnT achieve some breaking points. In the current popular frost/3 spender build however the attack speed increase to damage is negligible. So dont go out of your way to get attack speed. Dont sacrifice Crit/ChD/cold/sentry damage for it. But its not a useless stat. If its about paragon however go for IAS last. Cooldown reduction is actually better honestly to get your army out sooner.
Sentries do not benefit from AD, only your own attacks do. The only way it's of much use to you is if you use Kridershot.
Sentries benefit from IAS but there are breakpoints for it to change the amount of shots that sentries will fire. You only want more IAS if it will get you to another breakpoint. See this thread for the breakpoints with every combination of spenders: http://us.battle.net/d3/en/forum/topic/13271407601