I can write about 1000 rough words a day, if I've already done the data collection and crunching, and need to turn it into an argument. That's on a good day. I can't sustain more than about 3 of those a week.
If I'm revising work I already did, then I can redraft into cleaner copy about 5,000 words a day, assuming I'm not running around looking things up.
But I'm very productive, very efficient, very experienced, and I don't have bipolar disorder to deal with. If you can manage half of that, I'd say you're motoring.
I'd advise you to keep a productivity diary, of how many hours of genuinely productive work you manage per day. Not to beat yourself up with, but to learn your pattern and learn to accept it, and grab the good days when they come (some people have one good day every three or four days. I'm really lucky, I pretty much alternate productive day and faff day. If you only get one good day a fortnight, it will be a slog). On your less productive days, there are all sorts of things you can do fiddling with footnotes and improving the prose, which is not time wasting but not ready creative, and it's important to allow that time for your subconscious to be working out what to do next.
Take proper breaks, go for a walk, don't forget to eat and drink. Try different places to work (in certain frames of mind, I work in a cafe best, or in the library best, or in my office or on a park bench. Do whatever your brain needs).