I’d say it’s never too early to learn grammar, though I’ve found that I can only learn so much of it before I need to see it in context. The way I proceed is to read on grammar until my eyes start to glaze over and I start questioning whether what I’m learning is useful or not. That’s usually the point of diminishing returns.
Then I read Japanese content. As much as I can, without worrying too much about understanding the words. Whenever I recognize one of the grammatical structures I’ve seen, it helps give context to the lessons and gives me this “Aha! I know this” moment.
Once I feel I’ve internalized pretty well the 5-6 lessons I’ve read, I go back to reading about more grammar, then bounce back and forth with more reading.
I’m hoping as well that the Absolute Beginner Book Club will give me plenty of opportunities to both learn more grammar and to go much deeper into the grammatical understanding of each page. Having several dozen pairs of eyes all picking apart the same sentences will do that 
I’d encourage you to join the book club, seeing as it’s right about to start in a few days. The discussion alone will be worthwhile, not to mention the motivation boost of doing things all together.
Here are other resources you might like:
Organic Japanese with Cure Dolly
Tae Kim’s Guide to Learning Japanese
Bunpro
Don’s Japanese Conjugation Drill (Grammar exercise and practice)
I also know the Genki books tackle grammar, though having not gone through them I don’t have any opinion on them. Worth a try though.