The body of knowledge for FW 338.02 is sort of lost now – hard to comment on parameters. CoolTerm was the defacto ‘simple’ Gcode sender back in that time frame. RTS/CTS flow control generally worked better than Xon/Xoff, but both seemed to have driver dependencies and platform dependencies – not enough CPU to respond in a timely manner.
Most users seem to have different priorities than yours – they want to run long, intricate jobs and get maximum performance from tinyG.
Then, of course, there have been a whole lot of bug fixes and incremental feature enhancements to tinyG. The wiki has expanded a lot in the areas of status monitoring, queue management, etc, but frankly I am not sure there is a good way to tell you what might apply to 338.02.
Since you are a Java guy, you might want to look at Goko.com (google goko cnc), it is a new Java based project, again third party. Perhaps there is some knowledge there that will help you. I have no knowledge or experience, it showed up in a recent Forum post.
I’d highly recommend you shift your fw base up to build 440.20.
Virtually all the effort on fixes, and working knowledge of the community, is focussed on that build for now, and will be moving on toward further integration with G2 functionality.