Weird but not horrible parental situation

My parents (m51) and (f50) have been married since they were 18. They had three children (f26), (f24) and me (m18). My second sister (f24) found out in 2019 that my mom was dating some guy and at first she thought my mom was cheating on my dad. 

However it turns out they had been separated and my dad is ok with my mom seeing other people. We kids had an idea that they were separated as my mom would spend a large amount of time in the US while my dad lives in MRU. I basically saw her 4 months a year because I was going to school in MRU. My dad is the sole provider and has made a comfortable amount for our family. 

Since my sister discovered about this third person, this forced my mom to tell the children about the separation and the promise of divorce from my dad. However she told us we weren’t allowed to disclose the fact that we know about any of this to my dad. “Why don’t you just come clean and tell your dad that you know?” Well because we are worried that he might not carry out the promises he has made to my mom through the divorce if he finds out she went behind his back to tell us (the children) about the situation. I have no doubt that my dad wouldn’t go back on his word and that he will carry out whatever promise he has made but my mom doesn’t not trust him. 

Every time I talk to my dad I feel like shit. Him and I have a very close connection because he raised me during my high school life until boarding. He raised me from 13-17 years of age. Those were the most important years of my life and I will forever be grateful at how he has committed to raising me alone. Thus this trust we have developed feels like a burden as now I feel like I’m betraying him by not telling him that I know about my moms lover and about the whole divorce. The worst is during boarding school he would tell me how he felt lonely and sad when he came home to an empty house. That’s what kills me the most, knowing that my mom is living her life while he is suffering and I can’t even tell him to move on and start dating. 

I was processing and moving on with my life until tonight he told me that he was going to try to convince her to come to a family vacation so we could all be together again for the first time since pre Covid. I don’t know how to tell him no. 

This situation has caused a lot of anxiety problems as well as depression. I feel like I need to runaway, yell and just let out all frustration but I don’t know how nor do I know how to resolve anything. I have been talking to a counselor but I can’t reach out to them right now because I’m staying with my mom and I’m worried she’ll over hear.

Sometimes I feel the easiest thing to do is let go, I mean it’s so easy to take your own life nowadays especially with these fucked up gun laws in the US. I am staying strong and finding a way to eventually get out of bed.

What do I do?