Looks like you’ve figured out the oil type!

You do need the car level as possible to check the dipstick, inclines do make a difference. I’m not sure about your ‘up to operating temperature’ comment, (although I’m no expert), as that shouldn’t be an issue.

The important thing is to leave it a few minutes after turning off the engine before checking the level, this allows oil held up in the engine to drain back to the sump to get a true idea of the actual level. If you check it straight after running the engine the dip stick will read low, even with the correct amount of oil in there, and you could overfill the sump trying to top it up.

Overfilling the oil doesn’t do the engine any good, as you can damage the seals.

Finally, yes, you should keep the oil at the correct level between services. All cars burn oil to an extent, and IIRC VW’s tend to use a fair bit of oil. DO NOT wait for an oil warning light.