Forgot to mention squashes and melons are spaced in rows 4' apart. Like tomatoes.I crowd my rows closer. I like your wider spacing. But, I tend to crowd things to get more bang for the buck with my garden footprint. Does make it more difficult to move around. I tend to plant in "blocks" and beds.
Potatoes are planted 8 - 12" apart, with 2 rows 14" apart, then a 32" path, followed by 2 more rows. This allows me to get down the center between the 2 groups for bug control, mulching and early harvest.
When I do corn and potatoes together, I do the 2 + 2 (row) method, alternating potatoes and corn. Or sometimes 2 corn, 1 potato, 2 corn... Those 2 plants make fantastic garden buddies!
If you have abundant space, that certainly makes it easier to allow more space between rows. I envy these folks who can put their garden in the middle of a huge block of land... not at all encumbered by space restrictions.