So some evenings you work until 9ish or 10? On those evenings he does the bedtime, and then you could plan for him to sleep whilst you work.
We were in a similar situation to you when ours were small - our 4yo struggled with babysitters, though we eventually found some. Before that, however, I was the one falling asleep at 8pm, until a friend pointed out that it is a brilliant thing to do, planned, once or twice a week. Kids in bed, nice relaxing bath and asleep myself by 8.30 - I enjoyed the rest of the week so much more!
Second handy hint, we kept an IOU book. We wanted to go to the cinema, but the babysitter fell through - put it in the IOU book, to be cashed in another time. Want an evening in with a bottle of wine, but dh falls asleep - note it in the IOU book, to be cashed in another time. (I started it in pregnancy. Everyone else eating prawns/soft cheese/drinking wine today. I owe me a large dish of prawns . . .)
I struggled too with the lack of couple time during the gruelling years. We concentrated on having fun during the days, en famille, and just battled through. Now our two are older and flying the nest, I am pleased to report that it hasn't destroyed our marriage and we are now having fun catching up on all of the date nights we are owed. However, I do know people who drifted apart during this stage.
Keep talking to your dh. Recognise his feelings - "You are so tired, aren't you?" but also articulate your own "It would be nice if we could sit down and watch X with a bottle of wine, wouldn't it? Shall we aim to do that on Saturday?"