I also started working for myself last year so I’m familiar with rethinking my travel decisions.
Personally I’d avoid the 4.5 hour drive, specially if your main consideration is avoiding a connection in Atlanta. You’re going to spend most of the $150 in savings on the rental car change and gas. Not to mention all the more wear and tear on yourself tacking on a 4.5 hour drive that includes Friday afternoon Dallas traffic.
I would take the connection through Atlanta all day long.
Would you be connecting to the last flight to BOS in ATL? If not, it’s an even easier decision for me as you’d have some back up if something goes wrong with your connection.