Someone once asked...
Someone answered with kindness...
Talk to your superior about how you feel, if you can do so safely. They are a human being and will want to help, even if they might not be able to. If nothing else, they will be kind. No good business wants to lose a good employee - hiring is a nightmare! Talk to a professional about burn-out as soon as you can. It can be much more dangerous than it is currently (even though it sounds very bad) if it is left unchecked. I did this, and it cost me a lot of my life and a lot of money. I have found that just venting to a human an hour a week really does help. Talk to a doctor, and keep records of the conversation. I don't know where you are in the world, but it's a medical issue, and - in many countries - you cannot be lawfully dismissed for having a medical issue. But it's important to document it. Do all of the above - not necessarily in this order - and only then think about anything further. When you are burnt-out, your capacity to make rational decisions is severely diminished - as you are finding with your capacity for work currently. Thus, you should not make any rash decisions without you and your employer being as fully medically informed as is possible. You are currently speaking about taking on further burdens yourself - a more senior role, or clocking into the current role for months - solely for the purpose of taking a rest. This does not need to be your burden. Do everything I said as best you can - it'll take a day at most - and it'll work out much better. I'm certain of that.