The lethal dose is 5-10 grams, the recommended safe dose is 10 milligrams maximum. Between those points you'll experience some pain and stomach discomfort. Regularly going over the safe dose may cause some organ issues.
Basically, even if you swallow all your toothpaste you're unlikely to have problems unless your diet is already rich in fluoride, and spitting but not rinsing is fine.
Basically, even if you swallow all your toothpaste you're unlikely to have problems unless your diet is already rich in fluoride, and spitting but not rinsing is fine.