'12 - 335: Not making Operating temp and Expansion Tank Cap Leak

[Das86TurboII]

I've read several threads on problems associated with the 335 not making operating temp. I'm experiencing the same when the ambient temp is cold. Especially below freezing. I live in the mountains of Colorado so this is a problem 1/2 the year. I've replaced the thermostat twice. And replaced the WP. I'm also getting leakage at the cap on the expansion tank. See pic. I have replaced the tank and 3 caps. At ~10-15 deg the operating temp may not come off the bottom/160 mark.

Additional detail. When I bought the car the PO had a JB4 piggy back tune on it. I got in a front end accident. After repairs we could not get the engine to run properly. The WP would run continuously after shutting down and drain the battery. I took it to a good BMW shop in the Denver area and they couldn't solve the problem. Calls to JB4 were fruitless. They removed the JB4 unit. When I made the repairs I swapped the OEM radiator with a CSF unit thinking I would keep the JB4 tune and want the additional cooling.

I'm not running any codes. I have a BMW scanner.

A few questions:
1) Why can't the car get to operating temp?
2) Are there different temp thermostats? Can I program the temp at which the thermostat opens?
3) Ideas on why the expansion tanks leaks. Obviously there's too much pressure