Mikael,
I had the same symptoms of oil leaking you describe.
I thought I had a seal problem as well.
BUT, when I had the car on a hoist at a dealer to recharge the air conditioner, I was surprised to find out that oil was dripping from a few of the oil pan bolts. The car had the original oil pan gasket for 20 years (at the time).
For a quick repair (it lasted 12 years) I put the car up on my jackstands; got under the car; undid a suspect bolt; cleaned each bolt; sprayed brake parts cleaner in the oil pan bolt bore; Put gasket silicone on the bolt threads and reinstalled the bolt; Moved on to the next suspect bolt. I waited a day to let the silicone set up and ... Did not have a problem after that. All done without taking off the oil pan or engine/transaxle removal.
While it may be something else, it may be the oil pan gasket. Check the Oil Pan bolts.
About engine and transaxle removal. I have had just the transaxle removed (clutch job) and the engine transaxle combo removed. In my opinion the engine/transaxle removed together is the way to go.
HTH
B.G.
P.S. In Canada our driving season is much like yours.
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