GTV Extension: how long is enough to qualify for ILR?

[bess3]

Hi, I need some advice on how long to extend my current GTV so that I am eligible towards the end. I am on the 5-year route. Visa issued: 16 Mar 2021 | Date of Entry: 27 March 2021 | Expiring: 16 Mar 2026 

I was outside the UK for 237 days in a row (6 Dec 2023–1 Aug 2024). I am considering a 3 year extension until 16 Mar 2029.

1) If I stay within the 180-day limit in each rolling 12-month period from now on, would I be eligible for ILR by March 2029?

2) I am a bit unclear how the rolling 12-month window is calculated in this case and whether the Dec 2023 absence will still affects my ILR eligibility in Mar 2029 for ILR? Or Shall I consider extending 4 years i.e until March 2030 to be on the safer side?

3) Will extension be granted on top of current visa expiry date, if decision date is before the current visa expiry date ? I am planning to schedule my application and biometrics so that I don't lose any eligible days on my current visa.