Are -300 and +200 close or distant in betting?

That's wide because it implies a 7.7% edge for the book. For reference, a book's typical edge when you bet against the spread is 4.55%

See source for a decent explanation and a no-vig calculator. However, the overround (the excess probability) is not the same as book's edge like that page claims. Instead, you can find the edge by dividing the player's EV (average loss in this case) by the amount risked. And the page's remark about Pinnacle is a bit outdated, perhaps depending on the sport. When it comes to American sports, the sharpest lines these days are at Bookmaker (aka CRIS) and maybe BetOnline.

How'd you do in Math class ?

It is Gambling. No advantage either way. 

they are 500 apart from each other