How will a divorce impact my immigration status?

Since your current green card is "unconditional" that means your marital status does not affect your green card status any more. So whether you stay married or not makes no difference to keeping your green card. However, once you are separated, you will have to use the 5-year residency rule for eligibility for naturalization. If you are married to your original green card sponsor, and living in a viable marital union, you can use the 3-year residency rule, but even a separation may disqualify you from eligibility. My view is that people should genrally do the right thing in making their life choices first, and sort out the immigration details afterwards. So if the marriage is no longer working out, I would not advise staying in the relationship in order to cut two years off your citizenship requirement.