4) “Rivers run down to sea-level finding the easiest course, North, South, East, West and all other intermediary directions over the Earth at the same time. If Earth were truly a spinning ball then many of these rivers would be impossibly flowing uphill, for example the Mississippi in its 3000 miles would have to ascend 11 miles before reaching the Gulf of Mexico."

Yes, rivers run down towards sea level, but sea level is defined as a sphere around the center of earth. At no point on earth do rivers flow upwards according to that definition. Only high force, very fast (and short-scale) or extremely exceptional events like storm floods or tsunamis defy this principle over short periods. 

"If the earth were a ball then the Mississippi would have to ascend 11 miles". What the hell is up on a sphere? The direction perpendicular to the surface is simply outward. Which means that, with regards to that line, there's no climbing. There's only a simplistic drawing going on here. It's a sphere, it has rotational symmetry. So, your 11 miles of climbing is someone else's 11 miles of gently flowing downwards.

Why does Dubay think  the Mississippi would have to ascend 11 miles?  – as so often,  Mr Dubay doesn’t explain this, so it’s hard to be sure what his mistake is.

Perhaps this is about the oblateness of the Earth?  Oblateness is the very slight bulge at the equator. The answer is that water is subject to the same forces that the rest of the earth is. The equator is very slightly further from the centre than the poles because the Earth’s spin makes it bulge.

Ever watched pizza dough being spun out into a disk? Same principle, with very much less stretching in proportion to size. Guess what – the water is spinning along with the earth , so it’s also spun outwards very slightly. Water is subject the same forces – centrifugal force, which is actually inertia, so both earth and water tend to move outwards in a straight line as they spin.

Here is an interesting  discussion over at Metabunk, at

https://www.metabunk.org/debunked-rivers-flow-uphill.t7783/#post-186569

This is well worth a read to see the topic argued out with flat earth believers, and their miscoeptions explained.

More on the bulge: https://en.wikipedia.org/wiki/Equatorial_bulge

where it's shown that Dubay's figures are adopted without checking fromTerraFirma: The Earth not a Planet', a scripture-inspired book written in 1901 by David Wardlaw Scott.

https://ia800209.us.archive.org/6/items/cu31924031764594/cu31924031764594.pdf

And what a surprise;  they are wrong. The actual difference in distance from the earyh's centre is around 4 miles, not 11. It doesn't matter much,of course; both the surface of the earth and the water of the river are lifted by that amount because of the centrifugal force.  Nothing here is anything but what we should expect on a spherical earth