My issue with cart heaters is that after sitting in the warm cart and going out and repeating, well I get colder after a while when stepping out.
As for the cover, both of mine didn't cover the windshield, but the did cover the clubs and honestly this can be a pain and if not clised, seems wind is always at your back. To much of a hassle.
Layering is good, but this year so far nothing I wear is helping the hip or fingers. Hot ceramic cofree mug makes the fingers feel okay, they actually bend without pain. But even the hot patches on the hip haven't helped. A no hip golf swing looks pretty ugly, not to mention the poor results.
Now all that said, I may head out this morning, temp 37 f at 9am, no wind, but 20 minute hot shower (hip is movin) and two 20 Oz Hot cups of coffee, hopin for 9 holes.