Help understanding song titled 天嫁 天嫁 | Marriage of the sky
  
  流星划过天幕 | A shooting star streaks the canopy of the sky
  长长的慧尾 | A long comet
  冰雪溶化汇成 | Snow melts and becomes
  千年的泪 | The tears of a thousand years
  亲人捎来的龙达 | The dragon brought by close relatives reaches
  光耀苍穹 | The dazzling blue dome of heavens
  阿妈告诉孩儿 | Mother, tell your child
  故事的凄美 | The sadness and beauty of history
  
  那是天上的桌玛 | This is the 桌玛 of the sky
  骑着白驹要远嫁 | Riding a white horse wants to marry a wife from far away
  离愁有多痛痛有多浓 | The grief of parting is too painful and the pain is too dense
  那里的小草绿吗 | Is the grass there green?
  那里的天蓝云白吗 | Is the sky there blue? Are the clouds there white?
  那里的你 还像从前一样美吗 | Are you, there, still beautiful as you used to be?
  
  嗡嘛哩嘛哩班咩哄
  嗡嘛哩嘛哩班咩哄
  嗡嘛哩嘛哩班咩哄
  嗡嘛哩嘛哩班咩哄


So here are my questions:


What is the correct spelling of 慧尾? The captions of this Youtube video have 慧尾, but I found a Baidu Baike article which has 彗尾…
What is this 亲人捎来的龙 (dragon that close relatives bring in)?
What does 桌玛 mean? Is it one word or two?
The translation of the line 离愁有多痛痛有多浓 sounds just horrible, so what does it mean and how do I better translate it?
If I take it right, "to marry" is 嫁 for women and another verb for men, so why is the sky taken as female, with verb 嫁? (This question probably only arises from the fact that Italian and many other languages have "sky" as masculine gender)


Note: the last 4 lines are the mantra "Om mani padme hum" repeated 4 times, with "mani" repeated twice each time (om mani mani padme hum).
My take to this is different. 

'桌玛' in Tibetan is like 'goddess'.

We can seize the meaning of '天嫁' from this two lines, 那是天上的桌玛, 骑着白驹要远嫁. It means the goddess from haven will go to a marriage （on the earth）faraway from her home(haven) by riding a white horse. 

So, '天嫁' means the marriage of the goddess from the heaven. It seems that she suffered lots of hardship from there according to the song.