I need your kind advice about my long term residency (10 years) basis and i would appreciate for your honest advice. Here below my Tier 1 case history and questions.
Tier 1 History
1- Currently i have applied under the category of Tier1 Entrepreneur (50K) extension application on 7th of December which is still under process. I have submitted my spouse and 1 child dependent applications along with my application. We have applied for extension before our the expiry of our Visa on 10th Dec,2016.
2- We are a small Chartered Accountancy firm and we are 2 Entrepreneur Team members in this practice firm and applied Tier1 together and approved in December 2013. My team member got the ILR on the basis of 10 years last year as he completed his 10 years in May 2016. But he is still my business partner as we intends to move on for a long term basis. So, i have applied on my own for this extension application but send my business partner's details with my application(all evidences passport, ILR card etc)
3- I came as a full time Student on 19th April 2007 and my 10 years period will be completed by 18th April 2017. Please correct me if i am wrong i can apply for ILR at least 28 days before the completion of 10 years which is around 22/23rd March 2017. We have a clean Immigration history and there are no over stays or criminal history ever.
4- We have fulfilled all the Tier 1 extension requirements i.e Investment more than 50K, creation of 2 full time employees etc.. so not worried about these things as this forum was really helpful to submit my application.
Questions.
1- How can i vary the application from Tier 1 Ent to ILR and what is the process to do that?
2- When shall i vary my application, i mean by which date. Will it be after 19th March or any date before 19th March?
3- I would like to apply via premium application service but confused because what if my application is still in process and do not have my passport and all other documentation with me because they are under process till now.
4- If i go via premium service then how many days before i can book an appointment.
5- Both of my Dependents (wife+2 years only child born in the UK) have applied with me as PBS dependents because their Visas were expiring on the same date as mine. Would it be wise to apply my wife's extension as a Dependent with my ILR premium service same day? Because i assume she will be overstayed if i don't submit her application with mine. Am i right?
5- What is the procedure for my two year child application? Can i apply directly citizenship for my child once i get ILR status or is there any other status which i need to apply.
6- At the end about Fee, We have paid £3,612 for all applications plus £1,800 health surcharge, If i vary application and go via premium service then do we have to pay in full or the gap remaining fee? Will they refund us the health Surcharge £1,800 back or what.
I know the above are a lot of questions to ask but would really appreciate if some senior members can answer these questions. I hope it would really helpful for other members who are short of few months to complete 10 years legally.
I never applied via any Solicitor and would like to apply for ILR on my own with the help of senior members

Thanks for your time!
Many thanks