Salaam sister. Thank you for your question.
It is very admirable of you that you are turning to Allah for help in this situation as He is the one we should always turn to. We should always keep in mind that He loves us indeftinitely and always wants good for us and never wants bad for us. So He is never selfish in His love.
When one loves another truly, they try never to be selfish in their love.
You love Allah so much and Allahs pleasure is so important for you and you dont want to take any step which will not please Allah and so if u truly love the man, you should try (even though i understand it is going to be very difficult) and end things with him and give him a chance to live with his wife. Because by you two wanting to be together, he cannot fulfill his duties toward his wife properly and might even decide to divorce her, (one of the things that Allah despises so much) and thus is not pleasing Allah. And you dont want someone you love to go against Allahs pleasure when it is so important for you to please Allah.
My humble opinion would be to stay away from them and Allah will put love between them as He says in sura Rum/21
«وَ مِنْ آیاتِهِ أَنْ خَلَقَ لَکُمْ مِنْ اَنْفُسِکُمْ اَزْواجاً لِتَسْکُنُوا اِلَیْها وَ جَعَلَ بَیْنَکُم مَوَدَّةً وَ رَحْمَةً اِنَّ فِی ذلِکَ لاَیاتٍ لِقَومٍ یَتَفَکَّرُونَ
And one of His signs is that He created mates for you from yourselves that you may find rest in them, and He put between you love and compassion; most surely there are signs in this for a people who reflect.
By doing this, not only are you saving your dunya and your hereafter but even the mans dunya and hereafter for which Allah will reward you tremendously because He watches over us all the time and knows everthing about us.
وَاِمَّا يَنۡزَغَـنَّكَ مِنَ الشَّيۡطٰنِ نَزۡغٌ فَاسۡتَعِذۡ بِاللّٰهِؕ اِنَّهٗ سَمِيۡعٌ عَلِيۡمٌ
Should a temptatiom from shaytan disturb you,seek.refuge in Allah; surely He is Hearing,Knowing.
Allah tests those whom He loves, so keep in mind Allah loves you and is watching over you so keep your trust in Him and never lose hope. After every difficulty there is ease.