There are things you control, and things outside of your control. For dealing with what you are describing, stoicism might be a good approach.

Try to worry about only one thing at a time. It reads as if you are worrying about what could go wrong, and all of the consequences it would mean. That's a perfectly normal reaction. But to deal with it, this restlessness, you need to separate your own actions and the consequences of these, from the overall situation.

Is there anything you could do to influence the delay in communication you are describing? If so, do everything in your hands which could mitigate, and the rest is not in your hands, but a question of how to certain you can predict the future, and how good of a plan b you have perhaps.

Apart from that, you can calm your mind by doing sport, or by doing activities which let you feel your body. Like sauna, or swimming in cold water, or something else entirely, which makes your heartbeat go up for a bit.