Here is an example on the question:

Is this a theoretically correct way to construct tangent points to the stroke?
Actually the curves are not much of a problem as the 3D model will be based up on the nodes.

Here is a link for that in svg:
http://openclipart.org/people/Lazur%20URH/vopx2.svg

Interesting.

A lot of the terminology you're using seems to be coming from the world of 3D animation (something I myself used to do, but in the dark ages) which few type design people are familiar with, so it's a little hard to follow.

If I understand correctly that you want to do 3D calligraphy, I would say that -to make it more interesting than merely dragging along a blob to make letters- you need to analyze what makes 2D calligraphy more than writing with a ball-point pen.

I'm sadly not a calligrapher, but I've been paying attention, and I believe formal calligraphy is based on manipulating a one-dimensional shape (namely the flat, wide tip of a broad-nib pen) in one or more of three ways: translation (movement along the 2D Cartesian space), rotation and modulation (pressure = releasing more ink); note however that not all three of these are always used; also, in type what the pen wants is often ignored. Furthermore -normally- the pen is always pulled and never pushed.

Extrapolate these to 3D:
- The tip of your pen must be a 2D form. What shape should it be? Probably a parallelogram. But what aspect and cant?
- Translation is very easy - just add depth.
- For rotation you need two dimensions, not three: the direction the pen tip is pointing is what limits it to two.
- For modulation you need to figure in which dimensions the pen can swell. Is it two or three? Not sure.
- Lastly, what is pull/push here?

hhp

It might be more interesting to you here how the overall shape looks, so here it is:

This is for a plan on the 2D overall shape.

A simple serif "B" letter with a "°" mark, and only 2D positions of the pen is modulated, so no rotation or scaling of the pen during the moves.
But it's true the calligraphed could mean those as well.

Here is a render of the pen shape:

Here are two renders on the current model:

But these are not that important, considering if I cannot answer the question on a 2D stroke constructing, it won't look good in 3D.

Furthermore -normally- the pen is always pulled and never pushed.

In formal writing / calligraphy / interrupted scripts the pen is always pulled (downstrokes only as in n) and never pushed. But in cursive writing/calligraphy the upstrokes connect the downstrokes may be pushed (upstroke as in n). In informal writing / calligraphy / running script the upstrokes are always pushed.
The Stroke by Gerrit Noordzij may be an good read when you are interested in that subject.
Getting the tangents right is troublesome indeed. I wrote something about that subject on page 20 of my brochure entitled FF DIN Round digital block letters.

[to follow]

Can't say that I could show any huge step forward,
but reworked the original imagery of the letter at least.

writing process here

The original idea of this has to be postponed further on a bit, as the project went to something that has to be finished very soon.

Until I can proudly present some progression with it, here is a brief summary what has happened and what is happening with this:
http://