best path to collect withheld commissions - ~1,816.25 due now and ~11,113.35 pending - left company over 4 months ago - commissions due upon payment

If you are an employee (as opposed to an independent sales rep) you can file a Payday Act Complaint with the Texas Workforce Commission's Labor Law Department.  If you are not an employee, the only remedy you have is the courts.  A small claims court can handle claims up to $10,000.00 and is easily navigable by a person without an attorney.  Above that amount, you will have to go to one of the bigger courts where, although an attorney is not required, you ought to have one.