The link you are posting of Immigration Rules Part 8 refers specifically to spouse settlement visa issued BEFORE 8th July 2012. They are the wrong rules to read as they are not relevant to you at all.
The immigration rules relevant to spouse of settled person FROM 9th July 2012 is Immigration Rules Appendix FM - family life with partner., which clearly states you need 60 months in this visa category for ILR.
https://www.gov.uk/guidance/immigration ... ly-members
Section E-ILRP: Eligibility for indefinite leave to remain as a partner
E-ILRP.1.1. To meet the eligibility requirements for indefinite leave to remain as a partner all of the requirements of paragraphs E-ILRP.1.2. to 1.6. must be met.
E-ILRP.1.2. The applicant must be in the UK with valid leave to remain as a partner under this Appendix (except that, where paragraph 39E of these Rules applies, any current period of overstaying will be disregarded).
E-ILRP.1.3. (1) Subject to sub-paragraph (2), the applicant must, at the date of application, have completed a continuous period of either:
(a) at least 60 months in the UK with:
(i) leave to enter granted on the basis of entry clearance as a partner granted under paragraph D-ECP.1.1.; or
(ii) limited leave to remain as a partner granted under paragraph D-LTRP.1.1.; or
(iii) a combination of (i) and (ii);
You do NOT qualify for ILR as the spouse of a settled person until you have held the relevant spouse visa under Appendix FM for 60 months (5 years). There is no shortcut route if you change visas.
You also CANNOT combine tier 2 main visa holder time with ANY dependent visa to make up 5 years to qualify for ILR.
You either need to stick wait 5 years on your tier 2 and apply for ILR if you meet the requirements OR switch to FLR(M) spouse visa and wait another 5 years (2 x 2.5 year visas).
Eligibility
If you’ve got a family visa as a partner or spouse on the 5-year route, you must have been living in the UK for 5 years.
It does clearly state if you have a family visa as a spouse or partner you need 5 years.