I can't help too much with the current issues, although regardless of how minor you think it is, if you have visible algae and the experts here are recommending a full SLAM, I would go ahead and do it; it really can't hurt and you'll know you got it and are starting clean.
For next winter, my experience in our climate where we don't have to flush/truly close (first year pool owner, so take with a grain of salt!) is that if you can get under part of the cover, just maintaining the chlorine level is a good idea. With no cover, I was able to add 1 gallon of 10% liquid chlorine from Home Depot every few weeks (so cost less than $20 total for Nov-Feb) and stay above the min level. Since nobody's swimming in it to care if it's high for a while, I just put it in a gallon at a time. I know algae isn't supposed to grow at temps under 60 degrees F, but that's such a short time here that it doesn't seem worth risking.
I have had clear water all winter, including the couple weeks when I shut the pump and Polaris off because the leaves were clogging them, until I could get in with a leaf rake and clean them off the bottom. The water temp was in the 40s then though. I was wishing for a cover initially, but now I wonder if it's easier to just deal with the leaves than to wrestle a cover on and off (especially a tight safety cover) and still have to deal with the junk that lands on top of it.
