Keeping aside the precap and few minutes of the episode, everything was so natural. It is how you move ahead in marriage with you life partner.
We, audience or in a way the people who make shows and films romanticised sex a lot as if it is very elusive, very exclusive thing and once in a lifetime moment 
In most arranged marriages people have sex without "falling in love", it is always a physical attraction towards your life partner. No one waits till you fall in love with your spouse like it is been shown in TV/Movies. Eventually as you co-habit the feelings starts to build so probably when you do the deed later on there is love, understanding etc.
Coming back to show, I treat FaTejo's marriage as arranged one. Yes, Fateh initiated it as a jilted lover but it was decided by both the families and eventually agreed upon by both bride and groom. Fateh and Tejo knew what they were getting into as an adult. They both are responsible for this marriage and it is upon them how to keep it intact and take it forward. In their case there was slight twist where Fateh was getting married to a friend and his ex's sister. So it was most obvious he was going to see his ex around him and all the more difficult to move on but Tejo in a way made it little bearable for him as she was his friend first and wife later. Slowly as the day passed and when they got comfortable with each other, the line between best friend and wife started to blur. Fateh's caring nature and his physical inclination towards Tejo was quite visible so it was obvious for Tejo to start falling for him and eventually give in to his advances as her husband. For Fateh, we don't know exactly why he consummated this marriage as we have never been shown his views about the same. It was definitely physical attraction, probably the situation they were in and Tejo's consent towards his romantic moves. This night he wanted her really badly he got her with her own consent. There is nothing wrong in it as they are husband and wife & it is a natural progression in any marriage.
Problem with Fateh is that he is very undecided on anything in his life. One day prior he was obsessed with Jasmeen, next day he shown mirror to that same Jasmeen, another day he was lost in Jasmeen's thought and next day he consummated his marriage with Tejo. He is having this relapses too often to be in a stable relationship and now that he has committed to Tejo about their relationship by getting physical, it will make the situation worse if he happens to back out of the marriage to be with his eternal love Jasmeen.
Tejo is someone who is very romantic by heart though practical in her life decisions. Tejo trusted Fateh with her soul when she got married to him, she knew he is a nice guy who has his heart in the right place. She wanted to correct the wrong that her sister has done with him. She trusted Fateh with her heart when he started caring for her as a husband, when he stood for her career, her ambitions, when he started showing interest in her. She Trusted Fateh with her body when she gave in to his romantic advances and consummated their marriage. So Tejo is in this marriage with her soul, heart and body. If Fateh backs out now in this marriage, it is going to break Tejo like nothing else cause it is not only going to break her heart but soul as well. Tejo will believe that she was his physical need only for that night and nothing else, and she won't be wrong if she thinks that way.
The ball is right now in Fateh's court. One wrong move on his part is going to destruct not only 3 lives (probably 4 if Tejo gets pregnant cause of this one night) but also 2 families. Nothing will remain as before as Tejo is not Jasmeen or Fateh. She is strong willed girl with immense self respect to back out and never look back. So to convince Tejo otherwise is going to be herculean task for Fateh if he mess up like it was shown in the precap.
Mannat Har Khushi Paane Ki
Arjun
Cricket
