I’m on the border of 6a/6b in south west Ohio, Peas and potatoes can take a light frost you could plant them March 15th ish direct. You can direct seed the standard summer crops by that date, green beans, corn, lettuce etc. And I would challenge the belief you can’t pre start. I would look up “winter sown” where you start seeds in gallon containers and leave them out the second half of winter. The jug protects the seeds/ seedlings like a mini green house and they sprout and grow early in the jug until you transplant them. The jugs could just sit in the same garden space you will plant into in May ish. Then you could do tomatoes and peppers. My other tip would be to look for early varieties generally. Most types will have varieties that are early maturing.