2. In case I missed something, can the kernel of MMHMP3 be flashed to GSF b27 ? And where do I find a flashable kernel in that case ?
1. That information about the kernel isn't exactly accurate. It's something about the stock kernel, not the kernel it uses at the moment. Both kernels (this one and the one used in gsf) are compiled from burstlam's source code. They are very much alike.
Linux kernel is only small (but essential) part of Android system. Gsf is based on leaked Android 2.3.4, this is based on official Android 2.3.5.
2. No reason to do that.