Data limit can be increased with commensurate reduction in performance. Current limit is 5000 but that can be increased to whatever limit PowerBI has.
Adding all SD's onto one chart which might have say 20 different stages, would make the chart very busy and very slow on large data sets. The additional complexity has not been considered and is not planned.
I dont know what bugs are on Github. The control was updated in August this year (2018) so anything before that is likely to have some issues with bad data and failing to nicely reject it and few minor issues with mouse-over.
Many people have emailed me about the control and the response has been positive. Some recent tweaks to the x-axis labels to allow rotation were the last modification.
https://github.com/tcd1nc/PowerBI-Control-Chart