Hey Lou,
I haven't posted before, but have been following your story from the start. It resonated a lot (minus the actual chutney), but until now I felt I didn't have anything useful to add - other than I think you are doing amazingly, but lots of other people were saying that too 
But then I saw that you were asking for advice from single mums, so thought I should contribute.
I was in a very similar situation to you three and a half years ago. My ex DP walked away when I was 6 weeks pregnant (I was 33 at the time) and we had been together for years - though not actually TTC - that was a surprise.
Anyway, I had to decide what to do re the pregnancy, and I so, so feel for you - it was the most horrendous month I have ever had in my life. Similar to you, I knew that I was not THAT young, so this may have been my only chance, but also, like you, I really didn't want to bring a child into the world on my own, which would also have meant staying in contact with the arsehole who had dumped me when pregnant (as well as his revolting family - who I never heard from throughout)
I should also say, that things were slightly different for me, in that ex DP and I had had a very lovely first month of me being pregnant together - i.e. him buying me pregnancy books, thinking about names etc. So I had had some time to "enjoy" it before he walked out, which I know has been very different for you.
Anyway, I ended up walking into (and out of) an abortion clinic (yes, a proper abortion clinic) 17 times over the course of three weeks - each time with an appointment to go ahead with a termination. It was absolutely horrific - and my blood still runs cold when I think of that time. Not, I hasten to add, because I am anti-abortion at all - but just because of the appalling conflicting opinions I personally, was going through at the time.
My head was saying that an abortion was absolutely the right thing to do - wipe the slate clean, get the arsehole completely out of my life, meet someone new with no baggage etc, but my heart (and this was just me - I don't mean you'll feel the same) was saying no, no, no. And having spoken to other people since, I think that had a lot to do with the month or so that I had known that I was pregnant and that things had been good between ex DP and I - so I had been excited about the pregnancy.
I remember just wishing and wishing that someone could tell me what the right thing to do was - that I could be shown the future of the two different paths my life would have taken, and that I could have then made a rational decision based on that. I had loads of counselling, spoke to numerous strangers online, made list after list of pros and cons of both scenario - but those lists always ended up reasonably evenly matched. Very different pros and cons on both sides admittedly - but still lots of both. And I guess that's the honest truth. Whatever you decide, will be the right decision for you. Easy to say, but actually, I've realised, it's true.
Say you go ahead and have the baby, it will be fine. It absolutely WON'T be the future you imagined for yourself, but you are bright and resourceful and (sound) lovely, you have a great support network around you - and you will make it work. It will be tough re contact with The Chunt, but if you do want this, you will manage. And at some point in the future you will breathe a sigh of relief that you made the decision you made - and that you have a DS / DD.
But if you don't, you will hopefully meet someone else and at some point in the future, have a family with him, and then at some point you will breathe a sigh of relief that you made the decision you made - and that you never have to have anything to do with the Chunt ever again.
For me, the decision was made for me. I couldn't, just couldn't go ahead with the termination - and after all the failed appointments (mostly me running out of the clinic in tears), the kind psychologist at the clinic pointed out that maybe my heart / body / someone was trying to tell me something - and that I should maybe listen. I think they were a bit pissed off with me to be honest too. I don't blame them. I felt - and still feel - a bit cowardly about it to be honest though - I was incapable of actually "doing something" to stop my pregnancy, and hey presto, because of my inaction, 7 months later, I ended up with a baby.
Needless to say, my DS (now 3) is fabulous and I wouldn't change him for the world. For me, that (non) decision was the right one. But then, who's to say that if I had made a different decision, that I wouldn't be sitting here now (or in some glam bar, rather than on my sofa!) with a fab DH thinking "Oh I'm so glad I made that decision back in 2009".
You can't predict the future, you can only go with what you think is right - for you - at the time. Someone up-thread mentioned imagining the least worst scenario of two bad scenarios - I think that's useful.
As for the good / bad bits of being a single Mum. Yes, it's hard. I am very lucky that I have an amazing Mum and Dad and friends nearby who help me out a lot (emotionally as well as practically). Money can be tight. The responsibility is frightening at times. Sundays are hard, seeing "picture perfect" nuclear families together in the park (although you know they're probably not). Dealing with ex DP and his crap family is hard - but I am grateful they want to be involved in DSs life at all, so I bite my tongue, a lot.
But then there are great bits too. DS and I are very, very close, a special little two-person team, which feels great and I wouldn't change that for the world. I hear married friends bickering about different parenting methods, having to "look after him more than the kids" and essentially having all the same concerns I have - just different. Also, as others have pointed out, you really can't ever guarantee NOT becoming a single Mum at some point anyway - judging by the number of idiot men around on this board anyway!
In short, it's not the fairytale I'd wished for when I was 8 years old. But then, what is - and whose life really does turn out like that?! I am super lucky compared to many - and right now, I genuinely wouldn't change a thing. Someone wise said to me, that it's not the hand of cards you're dealt, it's how you play them that makes the difference. Whatever you decide will be right for you.
On that bombshell, I am SO sorry for the length of this bloody post - I really hope it doesn't offend / make things difficult for you, I just wanted to help. I know you have heaps of support, but if you did want to talk to someone who's been there, PM me. Good luck and look after yourself X