1) Sorry but may I get the name of the application you are using? I do not understand where you were going to "check". Please clarify.
In general, yes, WAAS will improve the GPS accuracy.
2) Unfortunately not that I am aware of. Feel free to contact iNAVCorp.com if they have any solution on this.
3) How much of the gap in seconds? For example, when you past a junction / cross road as the starting time vs. when it actually is reflected in the iGuidance moving map?
4) Ignore Power Save because it is only meant for customs GPS applications that will wake up and record GPS data in certain fix time intervals, vs. once per second update requires by most street navigation software. DO NOT alter this setting or you will risk getting more delays in getting real-time GPS position info.