What you describe doesn't sound sustainable; and I agree with others who are saying that it sounds like you're doing a lot of project and product management.
Biggest issue to me is: management expects that I keep producing at the pace I was before the promotion. That's literally impossible. They have given you a new role; which means you have new duties that require your time. Your direct coding output will reduce in order that your influence can improve the coding output of the other devs - that's how having a lead works :)
I think you need to have a talk with your boss about what they actually expect from you in the new role; and what you believe is possible without putting in longer hours. If the new role is just a ruse to get you to work unpaid overtime, it's exploitation plain and simple. I'm hoping this is not the case and it's just a poorly-defined new role, which happens a fair bit.
Go in prepared, though. Ahead of time work out...
You should really have some idea of a roadmap too, before you have that discussion.
Sketch out what you think needs to happen in the next two years. Increasing your planning window can be a good way to spread out work (does the R&D need to be done now or could it wait?); or frame questions of prioritisation. eg. if your team is struggling because deployments are failing and there's a high bug rate, it makes sense to clear the decks and do your quality processes and automation stuff first.
For the day to day stuff like reviews and helping people - have a think about how that is coming across your desk. Is it spread throughout the day? Is it causing a lot of interruptions? If so, set aside some time during the day dedicated to code review and helping people - and let them know that's when you will be doing it. For example you might say that you will do all your code reviews at the start or end of the day; and you will be available for pairing for the hour after lunch. During the rest of the day, if someone asks for your time you can check if it's drop-everything urgent; and if it's not (it almost never is) then schedule them in to a time slot that doesn't disrupt other things. Similarly, the rest of the day you ignore code review notifications. Give them full attention when you have the time.
Hope that helps! Last thought really is don't let this conversation turn into how you can't do any "work" any more. Your job changed. Your lead tasks are work, not just the individual contribution you have been doing. It's a hugely damaging misconception that "work" means "writing lines of code". The conversation right now is your previous workload was not reduced to accommodate the new/added workload; and you need to get that in balance.