There are three routes we can recommend when you've fallen far behind on an Anki deck. Gabe has tried the first two.
Route 1: Suspend and start over
Gabe did this with his Japanese in July of 2017, after a 6-month break to learn Spanish. In his own words, "I had around 6,000 overdue flashcards and I barely remembered any of them. Instead of spending days and days trudging through 8 months worth of old reviews, I turned off all of my old flashcards and started over as a new, intermediate student. I only focused on learning words I didn’t yet know, and what I found was reassuring. Every new sentence I learned involved a bunch of old words. And so in practice, studying new vocabulary acted like a really effective review of my old vocabulary. That made it pretty comfortable to get back into the swing of things, and I didn’t feel like I lost a lot, despite shutting off all of those flashcards."
Route 2: Re-schedule to delete your scheduling and treat everything like a new card
Gabe did this with his Japanese in February of 2018, after he got derailed, again, due to the Kickstarter. "Basically, I deleted all my scheduling information. You can do that by exporting all your cards and importing them again as a new deck, or (perhaps simpler), go to Browse, select all of your cards, Go to File-->Reschedule, Select 'Place at end of new card queue.' Then start it all over. This has been pretty sustainable for me in Japanese and I'm coming back to my former level, with a more robust study habit."
Route 3: Keep your schedule, just turn down your max reviews/day.
If you think you'll still remember a substantial portion of your cards, then you can turn down your max reviews/day substantially and see if you can maintain a review habit that way. You'll have to fine-tune that number of reviews/day so that it's manageable without feeling terrible.
Why didn't Gabe go this route?
"I didn't end up choosing this route for my own Japanese because Japanese is hard to retain and so my accuracy with those old reviews was like 20% at best."
We hope these ideas help! Feel free to try multiple routes (don't try #2 until you're sure you want to do it, or until you make a backup with your scheduling) and see which one works best for you.