Hi Ivan, in the manual from the page 89 to the page 93 you will find some refferences about the 109.
Oil temperature should be kept between 30 to 75°C and could be as high as 95 during very short periods.
The water temp should be kept under 80°C, 105 can be maintened only for very short periods.
I fly almost exclusively the 109, I had troubles with the engine too, but now, just by checking the temps I don't face any problems.
The never exceed rpm is 3000, and the max takeoff power is 2450 rpm and 1.45 ATA (well 2400 or 2500 are fine), so you don't need to go to 3000 rpm to have more power. Don't forget to anticipate yours accelerations and decelerations to keep your rpm in the sweet powerband (2200 2500). Map keys for the oil rad and for the water rad (normally 5-6 7-
. As said before you have an indicator on your left wing for the water rad position, and you can watch the position of the yelow lever on your left for the oil radiator.
In a dive the procedure is to cut the throttle an to set the prop pitch to 09:30.
I'm sorry but I don't know what are the limits for oil pressure but IIRC you have some white small triangles (marks), normally the needle should stay between them.
Here is a good page for some refferences about the 109 (E-4 but i think it's ok):
http://www.shockwaveproductions.com/store/solo/bf109/
Have fun.