I am just going to answer your questions and share my thoughts. I am a BW just so you know.
Is it possible to remain friend with AP?
This is a loaded question. Sure, you could stay "friends" with her. But why on earth would you want to? This is NOT a quality person. If you stay "friends" with the ap, you are still actively cheating on your wife, you know 'the best woman in the world (period)'.
Or transfer, quit my current job and absolutely no contact is the only way to go?
If you want to stop the A and figure out a path back to your wife and family and self-respect, then yes, this is the only way to go.
Is it possible to bring it to the grave without telling my BS?
Yes of course it's possible. But if you love her as much as you say why would you want her to have her entire life be a lie? Not to mention that by doing that, you're doing damage to YOU too. Secrets like that will eat you up from the inside out.
How to be "in love" with her again?
Maybe stop cheating on her? There's an old adage about the grass being greener where you water it. Right now you are pouring time and attention into the ap instead of your wife - so of course the ap is going to take precedence in your thoughts. Try refocusing that attention and thought on your wife.
My world will completely turn up side down, no question about it.
Yeah it will. But YOU have a clear view of it. YOUR WIFE'S WORLD WILL BE BLOWN TO SMITHEREENS BECAUSE SHE HAS NO IDEA WHAT'S THREATENING IT RIGHT NOW.
As the time being, I just can’t confess. I don’t want to turn her life upside down. Can’t destroy our "perfect" family we have, as seen by our circle of friends and family members.
Just my 0.02, but you not wanting to confess has nothing to do with your wife's safety and everything to do with you not wanting to deal with the fallout of your actions. I imagine that is very scary, but the decent and right thing to do is to tell your wife before someone else does (cus I guarantee your A is not as secret as you believe). And just saying, but you don't have a perfect family - NO ONE does, seriously.
What I can do now maybe transfer my job to somewhere else and cut all contact.
Yes. Please do this. And tell your wife.
Is it true that I have to confess? There's no other way around?
You don't 'have to' anything. You should because it is the right thing to do. You should because if there's any hope of your marriage surviving this, I promise you that those chances diminish every day you keep the secret from your wife.
Should I have "the talk" with my AP before we end it?
Should I mention about the job transfer to her before I do it?
Can you see I still have the tendencies to protect my AP?
Lil bit, yeah.
How could I Do that to a person who devoted her life for me and our family?
This I do not know - and this is the question you need to dig in to.
Guess what? Infidelity is 100% deal breaker for me. No question about it
I... have questions. Clearly infidelity is NOT a deal breaker for you so what does this statement mean for you?
OBM, you say you've been lurking for a while. We have any number of WS's on here that were right where you're at that have managed to regain their footing in their own life. Sometimes the marriage survives and sometimes it doesn't, but the more important part is that they find their way beck to living a life of honesty and integrity. If that is something you want for yourself, start looking to former waywards that post on here and heed their advice and lean on them for support. Your situation is not hopeless, even it feels very scary and out of control right now.
Keep posting, keep reading, and please PLEASE tell your wife - she deserves the truth.