Sorry, I didn't see this till now. Use the @username function to alert me through the message system.

That antenna should work, one on each side. You don't need two separate antennas on each side if you use this type because it's mimo. One on each would suffice.

But, yea you want one wrt1900 on each side of the bridge

You can run dd-wrt or openwrt on them. It comes down to personal preference honestly. Dd-wrt is easier IMHO to get more complex setups going with less of a learning curve