Hi Mary,
A few ideas from an also not-quite-European perspective.
You`re quite right on the gennaker / spinnaker question, but I think over the years the gennaker definition, among non-keelboat sailors, has come to represent any assymetrical spinnaker used predominately for reaching. I think the Aussies might call it the same, from skiff sailing where the assymetric really found it`s roots in modern high-performance sailing. The fact that, in cat-sailing specifically, our "kite" has become flatter than a traditional "spinnaker" has probably made the term "gennaker" more accurately define that piece of cloth out front that makes us go fast. Call it what you like, as long as it complies with the measurement rule, it will be F16 class legal. If Rick were to design a Hooter that conforms to the 75% mid-girth rule, it would be accepted as class-legal. (And I`d save up for one !!)

From What I understand the difference between dispensation and grandfathering is the fact that grandfathering is a more permanent form of inclusion in the class, and allows these boats to race on the "Closed F16 class" while dispensation allows boats a form of temporary inclusion that is open to annual review, and can only race in Open F16 events. SImply put, the Taipan has been given permanent dispensation ie it is grandfathered and can race in any F16 event, national, international with no limitations. (Although it has an oversize jib it has been accepted as one of the foundation boats.)
On the other hand the Mosquito has been dispensated, meaning that we can hold local and even national Open events, provided we welcome and allow ANY F16 compliant boats to enter. The Mosquito is dispensated for being under min. weight, but due to our much smaller sailplan, our ISAF/Texel rating is slower than that of F16, so we comply in that regard. But we can`t enter our boats in a World champs or international event. (Most SA boats are actually over min. weight fully rigged, it`s only the Aussies who build insanely lightweight boats. )

"3. I have a question about Section 6.1.3 "Both the SCHRS (ISAF) and Texel rating of the design must be equal to or slower than the rating assigned to the Formula 16 class."
And, of course, those ratings are subject to change based upon performance, so if your SCHRS and/or Texel rating changes, that could affect whether or not you can stay in the Open F16 class; right? "

Wrong here Mary, I think the US is the only country where you modify handicaps based on actual performance. Souns like a nightmare to administer.(Australia use the VYC yardstick, they might also do the same, not sure.)
ISAF and Texel use a system of measurements of the boat, and use a formula to calculate it`s potential speed relative to other known boats. Unless you change the boat, your handicap stays the same. I find this the most sensible route, it prevents boats being "ratings-beaters" and "rating-creep" due to inactive sailors in the class, or basing the class rating on the performance of a large group of below-average sailors. It isn`t faultless, but it works to a large degree. This is WHY the F16 class chose the ISAF/Texel systems, they are constant.
Furthermore, you can download the ISAF/Texel calculators, type in the specs of your boat, and you`ll have an (unofficial) ISAF/Texel rating. All it takes is a half-day of taking some measurements. OR send the specs of your boat to Wouter, he is working on a refined/improved version of rating system.

Hope this answers some of your questions.

Steve