Cancer patient, employer or individual marketplace insurance?

I'm 30 and I live in WA. I came to the US initially as an international student and have been here for more than a decade. I have had health insurance through my school/work, but I had been fortunate enough to be a very healthy individual, I probably spent less than $200 every year on health stuff (including primary care visits), so my experience/understanding of US health insurance is still extremely limited.

I was recently diagnosed with cancer. This week I got a $3000 bill for an injection, totally freaked out and called my insurance. They told me "most" costs would be covered after I meet my out-of-pocket maximum ($8000). This insurance plan is offered by my employer, it was the only option available (we're a small company, just 7 employees total), and I'm currently paying $100/month. So this means that I'll be paying a minimum of $9200 every year for a while… I make slightly over the poverty level limit ($65k) so I don't qualify for financial assistance through my hospital, but $9200 every year is like a fourth of my paycheck after taxes. I doubt I'll be eligible for Medicare or any other social security benefits, as I am not a US citizen nor have a green card.

I'm trying to find out if purchasing a individual marketplace insurance plan with a lower out-of-pocket maximum would help me save more money. It sounds like employer-sponsored health plans tend to be cheaper because they cover some of the monthly costs, is that correct? Would a marketplace insurance plan cost more for me now that I have a "history" of cancer? I'm also wondering if I should ask my HR about whether they can offer another health plan with a lower out-of-pocket maximum, but I don't know how much it would cost for them to provide another plan just for me, and don't know if me asking that would be out of bounds… If anyone has any suggestions or thoughts, please let me know, I'm trying to keep my calm here but the financial stress is really cracking me now.