It's unfortunate that you've exhausted the funds you so admirably put forth. However, the state's attorney must still respond to the motions the private attorney has already filed. If a public defender or court-appointed attorney takes over the case, they may be able to supplement those motions in writing if necessary, and will be able to orally argue them in court at the appropriate time. The judge in your son's case will rule on them at some point. I wish your son well.
You really need to talk to the Public Defender's office as soon as possible to see if they can help you in this matter.
The motions already filed do have to be answered, but with no one to argue them, your son is in a much worse position.
In the alternative, you might want to see if another attorney can work with you on a payment plan that doesn't require you to put up massive cash in the beginning.