If your 3/2 is a really good suit, it will most likely work perfect overall in these conditions.
If it is just a "normal" allround suit, it will be too cold, yes, and I assume it is, if not bought expensive and specifically for surfing.
A 4/3 will do fine for all your conditions, if you get a better and new one, not too warm and never too cold, and easier to get in/out than 5/3 wintersuits.
5/3 and you will be way too warm many days IMO, unless you easily get cold.
It will also be a PITA to get in and out of such a thick wintersuit, if you get to ride a lot - and I think you will when you learn this magic amazing addictive sport
Boots for learning yes so you dont step on something on the bottom, but boots not needed at all in terms of being warm, in 10-14 degree water (unless you are colder than the average).
A hood might be good in 6 degree air, but not necessarily needed either when your water is 10-14 degree, and you wont use it most of your season summer/autumn anyways.
We got somewhat the same climate here in Denmark as you have I think.
When learning you will be more in the water yes, but you will also work so much that you get warm and tired, so I see no reason to go for anything different whether experienced or learning.
Very individual "how much or how little" you need though, so depends on your personal "heat/cold" level.
I am very warm, and would never be able to use even a 3/2 in your conditions, only when it is at its coldest maybe, but otherwise way too warm for me.
If a cheaper allround 3/2 it could work though.
Others, especially girls, sometimes use a 5/3 all summer too
Regarding boots, the limit where most change to/from boots when winter or early spring, is around 10-12°C.
For me, as I am not as cold, it is just over 5°Celcius I change.
But this does not matter for you, as you should start with boots to avoid cuts in your feet.
Also, IF wearing boots, you dont need as warm a suit - meaning by taking your boots on/off later when you have learned, you should happily be able to cover your whole season with one good suit, IMO a 4/3 would fit by far most kitesurfers in your temperatures