Did I do the right thing of adding him as Accompanying me in Canada, even though he is already here and working under work permit with LMIA?
For what I've seen in this forum, there's mainly two pathways that you can take:
1. Apply together, hope to get invited with the lower score and, if getting ITA, follow the whole process together until you're both PRs.
2. Apply on your own, higher change of getting ITA due to higher score. Get PR, then apply to sponsor your spouse, wait for the whole sponsorship process. Longer path. What if your spouse's work permit expires at certain point and has to stop working? Can you sustain yourselves with only you working? Don't answer me, it's for you to think about that.
IMO, I would go with option 1 and I get my spouse to take an English text. Any score above CLB 4 for each band will give you additional points. Based on last year's draws, 518 is still a really good score.