Lippert Electric Jack & Inverter and CONverter issues

You said your batteries are "good just weak". That makes no sense. Which is it? Good or weak? Can't be both.
If you have weak (bad) batteries your jacks won't work because the converter can't supply enough current on it's own. The connection to the tow vehicle can't supply enough current on it's own either. Both the tow vehicle and the converter might get it done except you've got bad batteries also sucking down power and likely turning it into heat.