Slow Coolant Loss and Tank Coffee

[BoxsterSteve]

Mike,
Creamy brown scum in coolant reservoir is intermix of coolant & oil; also known as milk shake, typically something to be seriously concerned about.
It could be as simple as a failed oil cooler gasket to something as serious as a cracked cylinder head. Continued coolant loss and start-up smoke are mechanical warning signs.
Get it checked out at a mechanic you can trust. This isn't the type of problem that will go away on its own. You need mechanical intervention.
Intermix can destroy your oil's ability to lubricate and protect metal surfaces in your engine.
Get 'er fixed right so you and your wife can enjoy the car.
Cheers,
Steve