I am more familiar with the process in NJ, less so in PA. I have not been through an experience like yours, but did work in the family court system, so I have some idea of what you are dealing with. Regardless of the status of the marriage, your chidren are entitled to financial support. If you want a court to issue a formal separation agreement which would include specific financial obligations, you should call your county courthouse and ask them to direct you to the dept. that deals with child support payments. I'm not familiar with PA's family services bureaucracy, so I can't be more specific than that. Courts make these determinations based on the income of the supporting spouse, but the more specifics you can provide (bills, supporting paperwork for expenses, etc.), the stronger your position will be. You can represent yourself thru this part of the process. That will depend on many factors, including how comfortable you are dealing with bureaucracy, courts, etc. However, if you intend to seek a divorce, you really should plan to engage an attorney on your behalf.
I have so much sympathy for you and your situation. The emotional stress and pressure are quite intense and the added element of dealing with paperwork and a bureaucratic system compounds this. However, to ensure that the children's rights and entitlements are protected, I strongly encourage you to use the system, rather than rely on financial support from your extended family. God bless them for their help, but it can only be a short term solution and all it does is allow the possibility for your husband to shirk his financial responsibilities and obligations.
As far as taking your children out of the country, go to the US State Dept. website. There is a lot of information there regarding the documents and certifications you will need in a situation like yours. As you can imagine, the paperwork aspect will be tedious, but certifying your husband's absence could possibly grant you more mobility with your children.
I wish you the best as you navigate this difficult situation.