FLR (O) OR SET(O)FORM, CAME AS A CHILD

[OBAPJ]

Hi everyone,
This is my first post and I apologise if this is the wrong thread. I just need some advice.

I came into the country aged 11 in 2001 on a visiting visa but stayed on to live with my dad and swedish step mom, went to secondary school, college and now graduated last year. In 2006 I met my now fiance and looking to get married next year.

I got the family residence card of an eea in 2007 due to step mother. In 2008 my mom in back home died. In 2010 my father and stem mum divorced so i cant apply for permanent residence(i was told).
As my eea stamp is about to run out i went to a solicitor to decide what to do next as my relationship with dad is not great and he is not willing to help.
Originally i thought i could apply for ILR under the 10yr rule but it turns out that whilst I was living with my dad before my residence card in 2007 I had nothing else so basically i must have overstayed. I wasnt aware of this as i was underaged.
So i thought i could apply for ILR using SET O form under private life as i no longer have any links in my home town. My family are here and settled.
Solicitor suggests using FLR O form but it seems that for me to get ILR it may take 6 yrs. I have already comleted 5yrs under eu.

My question is. Is FLR O the right form if so is it possible that I may get ILR from that or can i use SET O. solicitor says he doubts i will get ILR as i have not stayed here lawfully for 10 years even though that was not my fault due to age and have been here for over 11years now.

Thanks so much in advance.