1. Where is that slow leak coming from? A slow leak when the motor is off/cold is a bigger leak when it's hot and you're driving. Keep in mind, the coolant system is pressurized. Find and fix the leak!
2. Do you have the stock thermostat in there? I noticed this past weekend on my bone BONE stock 99 LX, my cruising temps were 189. High? Eh, not really because of the stock (185* t-stat), but with the tiny amount of coolant that's in your (any D-series) motor, and being that yours is boosted, it will heat it up pretty quickly. I would put a 160* thermostat in your car. Today. Best mod I've done yet for my LS1.
3. Yes, the intercooler will impede air flow to the radiator. Hard to fix without some major modification such as V-mount style, or side mount. What fan are you currently running? One of the most often overlooked but very important pieces on any coolant system is the fan shroud. You will GREATLY increase the efficiency of your fan/radiator by having a shroud.
Hope that helps!