the tank is ok with being lower than the pump,it will draw ok with the height in the photo.The top of the tank is a bit higher than the centerline of the pump,you should be fine with it.Maybe shorten the suction hose if you can by moving the tank outlet to be more in line with the pump suction inlet and shortening the hose. I wouldnt bother with gauges for what you are running here,its not that complex of a system,simple open center valving and cylinders.If you are concerned,reach down and feel the tank when operating,if you cant touch it comfortably with your hand then you need a bigger tank with more volume or a fluid cooler to reduce the temps you are running..My rule of thumb always is (1gal of tank) for every 1GPM at 1000psi.Its always worked for me.I used that same formula for a no-talkie advanced research project at work,the tank came in at 270gallons..and worked like a champ.I wouldnt bother priming the inside now,it has fluid film all over it Im sure.Just keep it up to working level.
