SET(O) Online Form Queries

Hi,
My wife who is currently a PBS Dependant Tier 2 is applying to ILR using SET(O) online form. She and my two sons entered the UK on 18/05/2014. They got their last visa extension on 13/12/2018 until 06/11/2021. We are from Egypt and I entered the UK on 12/11/2012. I got my ILR on 22/12/2017 and became a British citizen on 10/07/2019. I have the following queries about my wife's ILR application:
1) Because ILR application costs are high, only my wife is applying this time. We plan that our sons (9 & 13 years old) will apply to ILR sometime in 2021. Does my wife's ILR application affect my sons' PBS Dependant visa in any harmful way? I've heard their PBS visa may be cancelled if she gets ILR on her own; is this right?
2) In the Finance section, there is this question: Do you or anyone else who is part of this application receive any public funds? Should the answer be Yes or No, given than I have been receiving child benefit for my two sons since January 2018 (i.e. after I got my ILR)
3) In the absences section, should my wife disclose only the absences after 11 January 2018 or all absences since they came to the UK on 18 May 2014?
Many thanks

1) Because ILR application costs are high, only my wife is applying this time. We plan that our sons (9 & 13 years old) will apply to ILR sometime in 2021. Does my wife's ILR application affect my sons' PBS Dependant visa in any harmful way? I've heard their PBS visa may be cancelled if she gets ILR on her own; is this right?

Nonsense. Nothing happens to their visas. You can however expect HO to write to you to ask about the children.

2) In the Finance section, there is this question: Do you or anyone else who is part of this application receive any public funds? Should the answer be Yes or No, given than I have been receiving child benefit for my two sons since January 2018 (i.e. after I got my ILR)

You an answer NO and then explain briefly if there is an 'additional information' section.

3) In the absences section, should my wife disclose only the absences after 11 January 2018 or all absences since they came to the UK on 18 May 2014?

Only absences from the date their last visa was issued.