ILR = Indefinite Leave to Remain, aka permanent residence (similar to a US green card).
FLR = Further Leave to Remain, aka a two-year spousal visa during which time you collect proof of an a on-going, co-habiting relationship with your spouse to use as evidence when applying for ILR.
As for your work situation - obviously I am not privy to the intimate details of your visa application, but I do know that many of us here who have moved over on fiancee visas (myself included) have been told in no uncertain terms that work in any form (US or UK, paid or unpaid) is illegal. I have never heard of a fiancee visa being approved on the grounds you've given - spousal visas, yes, but not fiancees. In my experience, the Home Office expects someone in your situation, who must work in order to support themselves rather than relying on financial support from the UK sponsor, to marry outside the UK, or on a visit-for-marriage visa, and apply for the spousal visa before taking up residence in the UK.
Again, I don't wish to challenge your account of your situation, as I don't have all the details, but your scenario is extremely unusual and I strongly suggest that, now that you're here in the UK, you speak to the Home Office again about your work. It's sadly quite common for the consulates to give VERY wrong advice, and I'd hate for any future visa applications of yours to be compromised by bad advice.