You might be able to get full child custody AND child support (even if you can't find him you can get the order and he will go into the dead beat dad database, eventually he will turn up and owe a lot of money). For $2000 sure. probably a lot less since it's practically uncontested. I deal with child support cases, give my office a call and we can help you with this issue.
Now in terms of bankruptcy? I don't deal with bankruptcy, but I recall bankruptcies going for a flat fee of around $1500-2500. So I don't think that budget is realistic for both items. I'm sorry to hear about your issues, and I hope you can find a way to get everything you need done so you can move on.
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In response to your question, (1) one can file for divorce after being separated for one year; (2) you can file for child custody now; and (3) bankruptcy is a different animal for which I can provide a referral. It sounds like you need to file for child custody, child support and an expedited equitable distribution. You will need your ex-husband's address in order to serve him with the summons and complaint. You don't mention spousal support, but perhaps you would be awarded some spousal support as well. This would need to be explored.