Yeah, nearby highs or lows would probably coalesce. You do get troughs instead of point (single area, actually) sometimes. Picture only the largest seas and landmasses as 'anchors' for highs or lows.

I think in winter the 'polar high' just extends its circulation further toward the equator. The polar outflow is comparatively dry, which is why Antarctica is technically a desert. Plus, the colder the water the less evaporates and the colder the air, the less it picks up.

Yes, the doldrums do migrate north and south some seasonally.