ILR inquiry eligibility and salary threshold exemption

Hello all, can anyone advice me as this is only my assumptions. I am planning to apply for ILR 5 year route within this month but not entirely sure with my eligibility.

Details are as follows:

1. Tier 2 General migrant
Validity: 01/11/14- 01/12/17
Job title: Public relations officer (2472)
-entered UK on the 4th December 2014

2. Change employer
Tier 2 General migrant
Validity: 04/01/17 - 22/01/20
Job title: Biomedical scientist (2112)

Question 1: Am I eligible for the 5 year route? I think I am but not sure if I'll count back from the time that I have entered UK or when my visa was approved.

Question 2: Am I exempt with the salary threshold? Currently, I don't meet the required salary but Biomedical scientist code 2112 job is on the PhD job list so I am exempt. Please correct me as I am just assuming.
Should it be the same job for the whole 5 year or they only consider my current job for the salary exemption?

Question 3: Can I apply together with my dependent (wife)? We have the same validity dates but under my PBS Tier 2 (General) as dependent.

Thanks in advance.

Question 1: Am I eligible for the 5 year route? I think I am but not sure if I'll count back from the time that I have entered UK or when my visa was approved.

You can apply for ILR no sooner than within 28 days before the 5th anniversary of your initial visa ISSUE date.

Question 2: Am I exempt with the salary threshold? Currently, I don't meet the required salary but Biomedical scientist code 2112 job is on the PhD job list so I am exempt. Please correct me as I am just assuming.

PhD jobs are exempt from the ILR salary threshold.

Should it be the same job for the whole 5 year or they only consider my current job for the salary exemption?

Current job and SOC.

Question 3: Can I apply together with my dependent (wife)? We have the same validity dates but under my PBS Tier 2 (General) as dependent

Yes, provided your spouse meets the requirements (English and LIUK, 2 year cohabitation evidence etc).

Thank you for the quick response.