This is where you run into building codes issues. Locking the handles together eliminates a path of egress, which isn’t ok. Installing an astragal and coordinator may be ok depending on the building capacity, because it requires people to use only on of the doors for ingress/egress which can also be an issue. It looks like you have an adams rite style bolt, so the most likely attack is a crowbar. A “J” tool, I presume you’re taking about a DDT, won’t work gear because you don’t have exit devices. Really the best thing you could do it get an alarm and a safe for anything highly valuable.