Here's my honest response as someone who is single at 34 (almost 35).
1 Do you think that one with AS should get married?
I've honestly felt that it would be unfair to a healthy person. I do not know what the extent of my illness is...if I will end up on disability eventually. I also can't imagine someone putting up with all my bizarro (sometimes icky) problems.
2 What will be the quality of life?
It's a toss-up. So many of us have completely different symptoms and levels. It also depends how well you take care of yourself.
3 What will be the quality of life if i follow NSD ?
Greatly depends. NSD did NOT show measurable improvements for me despite following it carefully for 6 months.
4 What is the quality of life with Anti-TNF?
I'm in a flare this morning despite Humira, NSAIDs, and prednisone. It reduces problems, but doesn't end them.
5 Can we provide everything to our better half?
No. But then again, no one could provide EVERYTHING.

6 Will AS (just AS in mind) cause any problem in conception of children?
No, but as AS is genetic, we will pass on our genes and proclivity to the illness. I do think you can improve your chances with careful nutrition and building children up properly.
I hope this isn't discouraging, but I wanted to be honest. Last night, I sat next to two friends who have such an enviable marriage. I drove home pretty sad despite my resolutions not to grieve any longer about being alone. When I stopped by the dance studio to pick up something, two of the girls sitting on the steps blurted out, "Why hasn't some guy snapped you up yet?" At 35, ill, and tired, I said before thinking, "I'm SICK. I have a degenerative illness." It actually felt good to admit. Other people have no idea the sadness we carry daily.
As a follower of Christ, I've learned to pray my fears and tears. When I start feeling sad/lonely, I remember that I'm fully loved and accepted. I think people with AS have a special place in God's heart--I've seen that here. When I crumble, it's amazing how God has lavished his love on me. I also preach to myself daily that I have all I need. When I doubt this, God loves me enough to find ways to remind me. As for my future, he's told us not to worry. I will continue to leave the details to him and follow him wherever that leads. That's true happiness.