Contact after 9 months NC

I share a child with my XN. I've been out of a relationship with him for over three years, since our son was 6 months old. I have joint legal custody and full physical custody. XN was only granted supervised visitations due to me asking him to take a drug test in court and he refused. He ended up admitting to it. He has also ordered to pay $300 a month in child support. XN hasn't seen DS since November 2010 and has only just asked about him 2-3 times since then. He moved to another state (10 hours away) in September 2011 with a woman he had only been dating for about 8-9 months. His girlfriend (wife, now) claimed the move was so that he could get a better job and because he father was "very ill." Child support payments have been very sporadic. Basically, I only receive it when DCSE catches up to him and withholds his wages. He is now $6,000 behind in CS. He has never spent a birthday or Christmas with DS, nor sent a single card or gift. Believe me, I am not as upset about this as you may think. I honestly AM glad he chooses to stay away because I know deep down that my son would suffer from his random appearance and disappearances and possibly the same emotional and mental abuse I was subjected to for the 9 years I was on and off with him. Since DS was only 11 months old last time he saw him, he doesn't remember him and still hasn't asked the dreaded questions "Who/Where is my dad? Why did he leave?"

So I typically get what I call "holiday harassment" from him and his family (they're all about as twisted as he is) through Facebook and e-mail. Oddly enough, last year I was spared (thank God.) They seem to only contact me when he is paying CS. His longest streak on non-payment of CS was from March 2012 until September 2013. In those 18 months, I NEVER harassed him or his family, or griped about it on Facebook. I let Social Services deal with it. He is currently paying weekly now.

Well, DS turned four on Monday. I log into my e-mail account yesterday morning to an e-mail from him Monday night (I suspect it is actually his wife typing) asking "Hey, can you tell [DS] I said happy birthday? How is he doing? Are you still getting the child support?"

I haven't responded because I don't even know what to say. Last time I heard from him before this was back in January when I had to get his permission to take my son on a cruise. He asked how he was doing and I decided to tell him about 3 sentences about DS (what he likes and things he does) and kept it at that. He responded back saying "oh, that is awesome! I'm glad to hear he is doing so well. I know things haven't been easy but I want to try to talk some more. I want to make up for what I've missed." I never responded after that. Again, I didn't know what else to say. Before this contact, I didn't hear from him for 15 months. That time, he sent 3 e-mails back-to-back-to-back between 7pm-10pm demanding "information" and pictures of "his son" and being nasty saying that he was paying child support and getting nothing in return. Four days before he sent that, I had just received the first CS payment after he had moved out of state.

This e-mail has sent me for a spin. Does he really think I sit my son down everyday (or even once) and explained this situation to him? Does he really think that he deserves that kind of recognition? I mean, don't get me wrong, if and when my son ever asks about his father, I will be as open and honest as possible. However, that is if and when HE ever wants to ask. Of all days, why would I just come out of left field on his BIRTHDAY and say "Hey, your dad wants to wish you a happy birthday!" Also, how do I explain how he is doing besides just "fine" or "okay?" Is he expecting a re-cap of everything he has done in the past 9 and a half months? Last, but not least, why did he have to mention child support in an e-mail about his birthday? I guess he is expecting me to say "yes, I am getting it now! Thank you SOOO VERY MUCH for helping my out!" WTF? I will NEVER. He acts as though he is donating to charity, not taking care of a human obligation he helped me bring into this world.

This is just a vent and a way to share with all you other moms that unfortunately have to co-parent with these losers.