If louvers are not what you pictured on the hood of your YJ maybe a cowl induction type of hood scoop would work to help reduce the underhood temps. Might be worth a try.
As to the high engine temps I tend to think they are a little high and maybe if the louvers/scoop don't help you will need something else. Do you have an auto or a stick? If you have an auto it could be eliminated from pre-heating the coolant by routing your trans fluid through its own cooler not the radiator. The next thing you can try is a pusher fan in front of the radiator to help when on the trail/rockcrawling. Last but not least would be to increse the cfm being pulled through the radiator by increasing the capacity of your current fan. All these things may have to be used together to affect the decreased temps you are looking for. Just MHO.