1. documented precision of Win7 Time Service: a few seconds (worse than 1 second). 2. ping compensation of NTP & Windows Time Service: certainly yes, already exist. 3. alternative NTP softwares: #to be answered by others#
Since I've answered 2 out of 3 of the concerns of your question, I'd prefer you update your question to narrow/restrict the scope of it, so that the bounty would really help solve your problem but not attract easily research-able stuff (which i already have done).
In particular I want answerers with actual experience in the 3rd party NTP softwares they recommend. Do you agree with that? Please also state your request to be included in the bounty notice.