What is the dividing line between support and enabling?

My spouse, who has ADHD, depression, and anxiety, seems to me to once again be floundering.  It became clear to me on one of his rare days at home (he spends several days a week at his elderly parents' home) that his symptoms are interfering with his well-being and functioning:  he is having problems sleeping, he doesn't get anything done when he's at home (I do all the chores), and his room is a mess.  There have been several instances of my spouse's treatment-resistant depression acting up over the years but I feel as though this time is a bit different, because the busy schedule that my husband has (spending time at his parents, where he accomplishes almost nothing for himself, and a part-time tutoring job, where he is paid to sit and wait for people to show up for help) disguises the fact that he can barely get anything done otherwise.  So, I'm not worried that he's going to plunge off the deep end but I do think that this is one of those times that a return to therapy is in order.  

Now, to my question:  I want to be supportive but I don't want to enable this frustrating, floundering existence by doing things that make my spouse think that everything is hunky-dory.  How best to not enable him but to not abandon him either?  Thank you.