Wow. His positive qualities must be amazing for you to still be with him. I'm proud of you, OP. But I have two words that you might like to keep in case things get worse: "Irreconcilable differences".

Which school did he graduated from? I want to know to NOT send my future children there for education.

Tell him to look up every known planet and star. Then ask him if Earth is flat again.

Of course the world isn't flat. If it was, cats would have pushed everything off it of it LONG ago!

so you didnt know until now that you married an idiot? how could you not know that?

Don't have kids...

Alright... I'm just going to write an argument and you can show him. Because why not, ignorance can only be cured by explanation. 1) THE MOON - Ok, so the first way we know the Earth is round is from our very own moon. Now I know your husband will probably contest the moon landing and all that, but that's a discussion for another day (in short, it would've cost far more time and effort to fake the moon landing than to actually go to the moon). Now as he probably will have noticed, the moon only appears at the bookends of the day, travelling in a crude arc. We can therefore either imply >that the earth is turning away from the earth as it is rotating >that the moon is only propped up at various times. The latter can be easily disproved simply by phoning a friend on the other side of the world and asking them if they can see the moon in the sky. The fact that the moon is always visible somewhere at all times assures us that the world is in some way rotating (the same goes for the sun). What's more, on some nights, much of the moon is obviously obstructed, by a clearly rounded shadow from the Earth (hence crescent moons), so showing the earth to be spherical. 2) THE HORIZON - Take your husband to the coast sometime and look out into the sea. When you see things emerge from the distance, be it a sunrise, or an approaching ship, notice how it seems to look like it is emerging from beneath the water. This is because the curve of the earth obstructs us from seeing these things any sooner, yet if you travel in a boat in that direction, you will know that submerging does not occur. This curve not only obstructs ships and the sun, but also stars, for the northern and southern hemispheres see different stars and constellations due to the curve obstructing some from view. It further explains why you can see further into the horizon on a cliff than on a beach, as you can see slightly further over the curve given your position. 3) GRAVITY - It has been scientifically proven that gravity pulls objects closer to the centre of the celestial body / object with the gravitational force. As the gravitational pull in every place in the earth is directly below us at all times, this implies that the gravitational centre of the world in directly beneath every corner of the earth and therefore this must converge in the centre of a spherical earth. Otherwise, the gravitational pull would be sideways as well as directly down. 4) TRUSTING PEOPLE - I know your husband probably doesn't trust the scientists and astronauts easily, but there a wide array of photos of earth as spherical objects. No astronaut or NASA employee or employee of any other space agency, of which there are many, has ever ever disputed the idea that the Earth is spherical. Maybe they're hypnotised, maybe they're all in a massive conspiracy, but seriously, what are the chances? Given all the evidence, there's no reason or motive to believe the world is anything other than spherical. There would be at least one angry former NASA employee exposing their deceit if we were being led on. And, I mean, they spend so much effort trying to research other planets, observing for example the patterns of moons in relation to their planets, or the rotation of other planets, a flat planet would be... a remarkable anomaly. 5) TRAVEL - Go in a plane. Aim in any direction you like, and keep going straight. You will end up at the same place you started eventually. If anyone seriously wants to prove the world is flat at all costs, surely disproving this would be their primary tactic? If you go high enough, you can even see yourself the curve of the earth below you. It might be a waste of your time and money, however, when so much other proof exists (just as I wasted so much time writing out this very obvious line of argument...).

Divorce time