My H too ... his little girlfriend OW did not want a relationship but is happy to keep things light. He experimented with that for a while and had/still has a huge crush on her. She is honest with him and tells him she doesn't want a relationship and is openly dating others, so he is too. But he is sad that she does not want to be exclusive. He is still interested in her but realizing that it is probably not continuing or getting more intense.
And also when he moved out he tried to get sympathy from me about how hard it was and how sad to tell his mom that we were splitting up, and how lonely he was. Um, sorry no I am not comforting you for the mess YOU made. I didn't ever comfort him I just ignored it.
Since I am a few months ahead of you I have a bit of advice for you. Do not make the same mistakes I made. And try what I tried that seemed to help my situation.
What was a bad idea? Whining to him about the OW. Being emotional. Being needy or clingy. Kissing some other guy in front of him (oops).
What was a good idea? Seeming like I was having a great life without him. Seeming like I was ok with the situation. Not always being available. Seeming happy and cool and mysterious. Seeming like I had changed some things he didn't like about me.
Keeping that in mind, my answers to your above questions are: 1. No way do not comfort her. Sorry she does not deserve ANYTHING nice from you right now. She is being a selfish bitch. Sorry. No. You don't have to be mean, just don't have time for her. She needs to cry alone. Preferably a lot of crying.
2. Exactly what Ahoy said. Focus on yourself and don't always be available. Take the advice people gave me which is to not contact her unless she contacts you first and to mostly not reply to non-essential messages or calls. I know it is SO hard, especially when you are trying to be the better guy. But unless the problem in your relationship was that you were too distant, you should do NC now. It works. And you don't have to do it forever. Let's say she sends you a message with some non-essential info. Take your time. Send her a message back the next day instead of right away. Another time just tell yourself you will not be replying to messages or answering calls for 2 days, and just ignore her unless there is an emergency. It gives you a feeling of control and makes her wonder why you aren't her puppet any more.
Oh and when you do communicate with her or see her do your best to seem upbeat, happy, relaxed and cool. My H seems to get tense when we don't talk for a while and when he does communicate he is cold and distant. But I take 2 approaches depending on the situation. Either 1.I am super short with my response, just one word answers, to show I'm not that interested in him or 2. I am very upbeat and friendly when he is tense. For example, if he sends me a tense question about logistics I will reply in a friendly happy way and add something like "good morning!" or "have a great day!" It seems to throw him off as he is expecting me to be angry, cold or negative. Always happy but not at all clingy.
I know it is so hard. Pick 3 small things you can do for yourself that will improve your life. Learn to cook a new dish, exercise, buy new shoes, learn to play guitar, get a new job, learn a new language. Take care of yourself.
You will feel up and down and a lot of crappy emotions. Keep focusing on yourself and making yourself better and at least at the end of the day you will be a better, more interesting person, no matter what your W does.