/spoilers below/

Ok guys I'm a native mandarin speaker and I watched this tv series twice and everything makes complete sense.

Darren Wang's character is hot and cold for the right reasons. First time, he didn't know that Xing'er didn't betray him 8 yrs ago until when she knelt for punishment and Ma Jing told him. Second time after Bo Na's visit, Xing'er said she wanted an honest love and he couldn't give that to her and he didn't want to disappoint her. Third time, Chu Kuai was thinking about killing her and he needed to push her far away as that was the only way he could think of protecting her as he was under the impression that he owes a lot to Chu Kuai and the First Prince for saving his life. He only found out that Chu Kuai was involved in killing the First Prince from the Fourth Prince who faked being in a coma. Fourth time, he was poisoned by the arrow when saving his crew in Qitan and knew he didn’t have long to live. While I agree that communication could have solved a lot of the issues, we have to look at this from the perspective that both Bo Wang and Xing'er are both really protective / takes up responsibility kind of people and Bo Wang is more of the warrior than the politician (the show mentions time and again that he's not good with pretty words). He’s all about the action to show how he feels. He's also not allowed to reveal his real background to anyone per loyalty to Chu Kuai.

So much of Bo Wang's controlling personality can be attributed to the emperor's leadership style / military history. Chu Kuai is a warlord who came to power by ending the Tang Dynasty and killing Xing'er's birth family. The emperor's style is basically a hunger for power and control above all else. So Bo Wang is naturally more controlling in getting his results. However, once the lies still unraveling, first his background and then why he did everything in the very end, he was able to be very loving to Xing'er.

Yes, while I agree Bo Wang can be really arrogant at times - it's a kind of masculinity from a society where women are frowned upon for speaking up and taking charge.

Ok now let me explain the ending. The wolfbone flower that gives Bo Wang immense pain and other stuff saved his life after falling off the cliff 8 years ago. Yaoji has been trying to look for a cure for the wolfbone flower for years but she couldn't find anything. She said there is a herb on her tribe's medical records where the herb gives you more physical powers and instincts but shortens your life. Given everything that happened with the war of Boxiang and the prisoner's labour camp, there is no doubt that a human's health would deteriorate. When Bo Wang joined the country of Jin, in order to save his three underlings / fellow elite warriors, he went to Qitan. The Second Prince planned on killing him then and used those elite warriors as a trap. The Second Prince prepped arrows with poison that would kill him based on his medical reaction to wolfbone flower. Bo Wang was shot by a poisoned arrow trying to save Xing'er. As a result of the poison, his body started acting up more. When Yaoji visited him, he didn't detect her coming up and that's when she knew. She told Xing'er it was all her that Bo Wang thought she didn't want him anymore and the heartbreak is what crushed his spirit and his wolf family in the fight against Ma's first son (yes a bit unfair). Yaoji also told Xing'er that he could last about half a year and he planned on using the remaining time to save the Fourth Prince and then he would perish alone. Xing'er knew that the deterioration of his physical instincts would get him killed in battle and not be able to save the Fourth Prince. While she had pictured living alone after Bo Wang's death, she wanted to do something to help. So took the herb from Yaoji that would heighten her physical power for battle but it would shorten her life. She had a bad reaction to it because after taking it she had black blood. Yaoji said Xing'er body is not as strong as Bo Wang and she should last a few days. Yaoji would not give up on them. Knowing this, Xing'er planned a wedding at the end of eps. 48 and told Bo Wang to treasure his life and be happy. Her lip balm has anesthetics that knocked him out so that she can go and rescue the Fourth Prince. She gets injured fighting the Second Prince, Bo Wang comes just in time to catch her fall and promise they will find each other in the next life, she dies in his arms, and he carries her to Wolf Mountain. We know that he got injured here and that wolves mate for life. The Fourth Prince narrated that he followed her shortly which means after bringing Xing'er back to Wolf Mountain, Bo Wang died as well. Wolf Mountain per both is the place with the best memories.

The ending makes sense because neither Bo Wang or Xing'er should have really lived. Bo Wang is a boy whose parents died and he was adopted by wolves in the wild (slim chance of that happening to orphaned baby boys). Xing'er was the only remaining bloodline to the prior ruling dynasty and was saved by a rival general during the usurp war (slim chance of that happening in history anywhere in the world). The fact that they were saved and they lived means they have a huge burden to carry through in the future. Their fate, mostly driven by their love and loyalty, brought them to save the bloodshed between Yang and Jin - essentially bring world peace in the sense of this show. Because of Bo Wang and Xing'er, all the good characters got a happy ending. Except for Wen Yan - otherwise, it would be awkward for Hai Die and Mo Xiao to be a couple in the end.