Am I understanding this correctly?

It won’t let me select two flairs, but I want to make sure I am understanding this correct, my employer offers insurance, which I currently have my plan through them. I have not found it to cover a good deal of my expenses, so I had already been thinking I would look into the marketplace during open enrollment. It also happens to be open enrollment for my employer and I found out the cost of my insurance plan is going way up. The lowest monthly premium is $540, for this job I make $20/hr for 9 hours a week, then the remaining 31 hours my rate is $18.50/hr (this is based on funding for providing different services habilitation vs attendant care/respite). I do also work for another company for an additional 18 hrs/week at $18.50/hr. Based on what I have seen I believe I would qualify for savings on a marketplace plan due to my employer’s lowest offered premium being more than 8.79% of my monthly income ($540 vs approx $4708.17). Am I understanding this right? I get lost in the jargon and when I filled out the application for the marketplace there never seemed to be any place to check for this, though I suppose I should have selected I wasn’t eligible to get insurance through my employer? I ask because even the marketplace plans are fairly expensive.