Luggage should be checked through on the outbound to EZE but you will have to collect it coming back to the US and recheck. I would be comfortable with 1.5 hours but if there's a problem somewhere there's not a ton of room for correction. If that worries you take the 3 or 4 hours. In the end, nothing's guaranteed.

You will not have to go through security again on the outbound, but will on the return. On the return, you will pass through immigration, collect your bag and pass through customs, re-check, then pass through security again to make your domestic connection.