Get back to the basics...
The difference between 4th and 2 and 4th and 3 is one yard. If you can't cover that one yard, you probably shouldn't worry about covering that 0.5 yard. From my 35 I'm running on you 4th and 1, from the 50 I'm running on you 4th and 2, and from your 35 I'm running on you 4th and 3. In the playoffs, they move back even further.