I totally understand. I have been in similar situations as well. That is good that they are willing to give you whatever resources you need to get the job done. Unfortunately it also seems like you are the what we call the “single point of failure” as well, which means all the project knowledge is in your head. So with out you the project is pretty much just dead. That is a good spot to be in for job security but a terrible place to be for work/life balance.
My suggestion would be to escalate the project delivery date as a risk every single meeting and in every communication that you send on the subject. Also escalate that you are the single point of failure and that situation needs to be remedy ASAP. That way you are covering your rear end if the dates slip and the deliverables are not ready or not as expected.
Hell yeah, that sounds like an excellent way to spend the day!