Oh gosh, I've been in that scenario as well, only it was a very long time ago, and I have one child rather than three. My heart truly goes out to you. But you know, you will discover that everything falls into place as it should. I dealt with lawyers during the divorce, issues over splitting assets (not that we had much of anything really), and issues with him not showing enough interest in his son. Also dealt with having to find employment and all of the other things we go through in life. At times I felt incredibly alone and just wanted to cry, but you know, it was my son I think, who gave me the strength to continue on. And I discovered just who I really was through all of it. You will be finding the same thing...you'll find your inner strength, and you will go through days of stress and days of laughter too. You'll find that there may be disadvantages to both parents not being there, but at the same time, in some ways it's easier (for example...when children don't have two parents they cannot get away with nearly as many things...lol).
I didn't have shared custody in my case; I was the sole custodial parent, with his dad getting him on weekends (or so the court ruled...he rarely did use his visitation rights). My sister, on the other hand, has shared custody with her ex and they do it a bit differently. It's sort of a 'day on, day off' kind of thing, where they go to one parent's house one day, and the other parent's the next...and weekends get rotated (one gets them one weekend and the other parent gets them the next). Their arrangement seems to work quite well, even though the parents don't get along.
Financially, it was hard for me at first, but I did get some help. My ex and I broke up when I was still pregnant - and the two of us had been temporarily staying at my dad's house at the time, so my ex moved out and I stayed there. I did wind up having to get Mother's Allowance (sort of Unemployment for single moms) for the first couple of years, but eventually I got back to working, first parttime babysitting, then into fulltime retail. Had to juggle babysitters for a while when I moved to a new province, but there was always something come up to help out if I was stuck. It's great if you have some sort of support network...when I moved I didn't really have that...so if you have lots of friends and family to support you, don't be afraid to take them up on any help they offer. If not, seek out support groups in your area; and if you can't find one, you could even try and create one by advertising...you know, a lot of moms offer to watch one anothers' children, or offer emotional support, etc. And that can be a huge help.
I'm sure you already know this, but as bad as the childrens' dad may be, I highly suggest they never hear anything negative said about him from you, or from other family members. Children are just so good at thinking they are to blame for all that happens between their mom and dad, and when one parent leaves - no matter the reason...it could be divorce, or even the death of a parent - they feel abandoned by that parent and tend to blame themselves. So they need to hear as much positive as they can...they need reassurance that their lives are stable, and that the parent they are living with is not going to leave them, or become overwhelmed with stress and worry.
And I think you're going to find too, that as your children grow they will be a great form of support for you as much as you are for them. I really do wish you the very best, and if you ever need someone to talk to, or just someone to listen, please don't hesitate to give me a shout. :hug: