Experience reneging on offer? Accepted an offer, two better processes still alive

Accepted a Dallas infra analyst role like two weeks ago, comp's capped but it's a good role. Problem is 2 Chicago processes I figured were dead are both still alive. Just completed final round superday at a renewables developer (cap markets role) this week, still waiting to hear. A PC associate role at a MM lender just moved me to a final round next week (highest comp).

The Dallas job sent over the employment agreement and negotiated some of the language. They haven't pushed me to sign yet but I figure that's coming any day (start date's mid july / 4 weeks from now).

How long can I sit on an unsigned employment agreement before it gets weird, especially when they haven't even asked yet? Do I just wait for them to bring it up or should I sign it and keep planning for the Dallas role? And if I do sign the Dallas contract, and Chicago comes through after, how screwed am I for backing out before I even start?

Anyone have any similar experience on reneging? Kind of stressing, appreciate anything.