I do use a circular saw blade from stew mac, although not with a table saw (I use my sliding miter and jig). Yes, I slot with a square fretboard blank (I square one edge and this is my reference edge throughout the slotting and tapering process). Some people may actually choose to slot with a pre radiused board so that they can maintain a uniform slot depth for the fret tang referencing the radiused surface(what you are calling kerf* these are not really relief cuts so you will find most people call them fret slots FWIW). If you slot without referenceing the radius, you may have to adjust the depth after radiusing or leave an extra deep slot (some feel that is sloppy, others see it as acceptable).
With regards to tolerances. Yes we work in thousandths. It may seem silly because wood expands and contracts with moisture levels, but you will find some parts require this level of accuracy. If you are working with the shape of a body, not a big deal(at least at the level of thousandths of an inch). If you are working with a neck, yes thousandths count. Positioning the frets as accurately as possible is something we try to achive. You will find that the scale used and fret positions are not perfectly located because of variables that are unavoidable(such as the act of fretting a string, which raises the string tension). That said, we adjust the length of the virbrating scale to get the fretted note closer to accurate (called adjusting for intonation). Some people do not try to adjust fret positions to take any of this into account, some will actually make very small adjustments in fret locations. By misplacing a fret by a few thousandths of an inch, it may only through you off by a cent or less, but do to the inhearant inaccuracy you are fighting you may already be a few cents off and this make the situation worse. Best bet is to try for as accurate as you can be.
Since we are chatting about accuracy. Take a look into setting up a neck, and the tolerances that we try to achive. You will adjust a string nut so that you have .005" clearance over your first fret or closer. You will allow for .010(high) to zero relief in the neck itself. Some people prefer to achive very low action(depending on the string 2-4/64ths) average (3-5/64ths), and given that a strings vibration(depending on how hard the player plucks the string) will account for just about all the clearance allowed for you are dialing in the action to just a few thousandths tolerance. Good things to keep in mind when constructing, and choosing material. It makes some of the things that may appear on the surface to be overkill, a little more easy to accept. I can absolutely promise you I work in thousandths on my acoustic guitars on even more parts of the instrument.
As for the Carbon fiber. It is becoming very common to use it on instruments. Especially on necks. You may want to consider the orientaion of the material you add, with regards to the planes that will resist the most force, and are most critical in terms of functionality. A thin flat laminate placed parallel to the fretboard is going to be of marginal value, perpendicular to the fretboard will add significantly more strength and stability as it relates to the strings and fret to string tolerance(speaking to stability).
With regards to laminate necks as you describe. There is a company that has been very big into laminates similar to what you describe (for the life of me I can't recall which company right off the top of my head, but it is a major brand). Maybe someone will drop the name of the company I am trying to remember here (think big on Spruce laminations).
Peace,Rich