Sophia, as your husband said, these aren't "real" words. They are spur-of-the-moment creations, and the basic "rule" (I'm inventing one) as to whether you can just add a -y, is probably (1)whether it sounds right and flows easily off the tongue and (2)there is no loss of meaning.
Some are so convenient as to have become legitimate, and I can think of many ending in d, or t: seed - seedy, greed - greedy, bead - beady, meat - meaty, salt - salty, sweat - sweaty, etc. Others just don't work, presumably because the meaning would be unclear: feed - feedy, feat - featy, bald - baldy.
Are these "legitimate" words? lemony, sugary, peppery, yeasty, softy (hardy is). I don't even know, but if you hear them you know what they mean.
This is kind of a loosey-goosey explanation, I know.