1. Dear Alex, I regret to say you will not be able to apply successfully for Indefinite Leave to Remain at this juncture. This is because you are not able to combine time on a Tier 2 visa with time spent on a dependency visa to gain the necessary five years continuous residence which is necessary for ILR. Here is a link to a page which sets out your situation https://www.gov.uk/settle-in-the-uk/y/you-have-a-work-visa/tier-2-general-visa. Be aware that the law was changed in 2012 to this more restrictive approach, Previously it was possible to combine the two visas together to gain the necessary five years.
2. At this stage, you will need to work on the Tier 2 visa until you have reached the necessary five years continuous residence. Then you can apply for ILR on the basis of your five years continuous residence. However, you will need five years on that type of visa.
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4. The pathway option is to work for another two years and three months and reach the five year threshold, as the answer suggests in point 2 above. 10 year options only arise if you spend more than 3 more years in the UK, which is the longer option.