Re small water leak. I've been chasing a start up leak on mine pretty much ever since I got it. Six years and 15,000 miles ago. (I don't get out much!) Takes maybe 5 to 8 starts followed by at least enough run time to get the engine up to temperature to drop the level by around 3/8" give or take.
So far leaks identified and fixed, more or less in chronological order, are water pump gasket (twice), all hoses, manifold heater and water pump itself. All added bit more loss but that darn start-up one is still there. I'm pretty sure previous owner or service guy put radweld or similar in to hold it because it didn't appear until after I'd changed the coolant shortly after getting the car. Getting to the point where I'm tempted to do same. Dye treatment showed up the other leaks just fine but not this one.
Hopefully now personal circumstances have changed I'll be able to give it some carefully watched long runs and verify that leak is independent of distance.
Don't think I have a filling / air entrapment issue. I just disconnect the small pipe from the top of the radiator, fill slowly via expansion tank start engine, top up and re-connect pipe when it stops taking more coolant. Usually about 1/4 pint extra needed before I reconnect the pipe. Pressure cap stays off until the temperature gauge moves. May need a touch more after a short run or may not. Probably helps that I do such jobs with the car facing down on a sloping part of the hardstanding in front of the house. Perhaps 1 in 20 or 25 slope with very slight fall to passenger side too.