1 I-frame per second is a general rule of thumb and common default setting. However, with smart codecs, I-Frames are now dynamically adjusted and often as infrequent as 1 every 10 second (or 300 frames if you are streaming at 30fps) when the complexity / action of the scene is low.
Generally, I would recommend switching from CBR to VBR and turning on smart codec. Most cameras we test today work well with those settings but I, of course, cannot vouch for this specific model. If you do try those settings, I would be interested to hear how it worked.
Btw, I do wonder if slow video recording is an issue with the SD card / edge recording.