While you’re correct about the gravitational situation - the outer and inner equators will have the highest and the lowest surface gravity, respectively, and the radius that corresponds roughly analogously to the North Pole, at 90 degrees between the equators, it would feel as though the ground was slanted somewhat, with downward being toward the outer equator. However, it does not follow that therefore everyone would live at the equators. It is perfectly possible to live on a hillside, and this occurs in many place on earth, such as these places:
I’ve not worked out the numbers yet, but my gut tells me the apparent “slant” would not be very steep, perhaps similar to a hill with a 15-20 degree slope.
Oh and I want to correct myself. Thinking further, I realize that at the “north pole”, the ground would seem to slant down towards the inner diameter, not the outer. If you placed a ball on the ground there, it would roll towards the inner equator, with a relatively small acceleration, because the center of gravity would lie in that direction.
Since magic is the only force that could create, or maintain such a planet, it obviously would be the ruling force of the entire region of space. Given that explanation, down can be arbitrary for any point on the surface, and the weather would be as the spell caster desired.
I imagine that day and night would be an “on/off” sort of thing, that being the simplest solution. Or, rotate the torus around the perpendicular axis through the hole. This leaves the center facing surface dark, unless the axis is inclined to the ecliptic enough to allow day night cycles. Given that gravity, and astronomic phenomenon must be magically controlled, I suggest that they be constrained to act in accordance with the book by Newton, except that Up and down be perpendicular to the plane tangent with the circular cross section of the local tubular region, not the body as a whole. (This has the advantage of matching the peculiarities of your mapping convention.)
Ringworld isn’t toroidal, it’s a ring. There’s no gentle curve from the inner surface to the outer surface. It’s more like a rectangular prism that’s been curved around into a circle. The walls are flat.
That’s not necessarily true. As long as the interior of the ring was sufficiently rigid to prevent collapsing, it would maintain itself. The water and atmosphere aren’t going to migrate into the “donut hole”. The gravity for their area of the ring would overrule the gravity of the other side since it’s closer. You could have a rigid core covered with dirt, water, and whatever else you wanted and it would maintain its shape.
Creating such a planet would be far beyond our technology and probably will be for hundreds of years at least, but it is technically possible.