Oh gosh you're in winter hell with heavy wheels. No wonder your car is struggling.
What I did when I lived in Ontario was I got a set of Civic VX rims with all seasons on them. But it would be better if you got snows on them. The lower rotational mass on the VX rims helps counteract the fact that the tires aren't low rolling resistance.
Getting the missing aero taken care of will help too but the wheels are definitely what's killing your ability to stay in lean burn.
If you have time to read 6 pages of posts
I talked with the guys on Insight Central in 2016 about this same issue. I also made a new post today about using 4th gear in lean burn, but that still might not help because of those heavy wheels.