I am very afraid of violating my faith of being a Catholic
If you are alone at the moment (not in another relationship) then you are not violating
your Catholic faith. As the things are, he is still your husband even though he left you
for another woman, as far as the Church is concerned you are still married.
Does any one know if decree of civil separation enough for me to petition my annulment at the RC church in Poland?
No, it's not. There is no such thing as divorce in RC church. There can be
an announcment of marriage being void (as never being valid for many reasons).
But if your marriage was proper, with a church ceremony and consumated then
there is no such thing as "divorce" for that kind of marriage.
Since we are not divorced, will it take longer than 2 years to complete the whole process?
Why do you think there should be an annulment of your marriage? Because of your
husbands betrayal? I'm afraid that's not a good enough reason. You have to realise
that if you don't get the annulment and enter into a relationship with another man,
that will mean living in the permanent state of mortal sin, not being able to receive
Holy Communion and generally being on the straight road to hell.
I'm not saying it's right (depends how you look at it), but these are the rules. Sorry.
BTW - your husband is in a worse situation then you, because he broke the Holy
Bond of Marriage. In other words - there is a hope for you, but if he doesn't come
back to you and repent - he's pretty much f*cked (even if he remains alone, but
if you remain alone, you'll be all right, as it is not your fault that he left you).
So, if you were wondering who's closer to hell at the moment - it's your husband.