First Rocket Design

If you're going to fly a C5-5, then make your rocket big enough to track and not go so high it drifts out of the field. Especially at Acton.
But if you can keep it to around 300' you should be OK as long as it isn't windy.
If you can 3D print a nose cone, you might want to consider printing up an entire "fin can" like the one supplied with the Alpha III kit. But you'll want to use a standard engine tube and centering rings so the plastic won't melt.
My approach to designing rockets so far has been to "clone" out of production kits using parts and plans, or to modify an existing design. For example, I recently modified a Red Max kit by adding a section of body tube with a stage coupler and installing a three engine cluster mount. Last year I made a boost glider loosely based on the old MPC Flat Cat.
It seems to me like you need to learn more about rocket parts and how they work. The Estes catslog has some information but there's plenty more available from many sources online.
II've been using this website for rocket plans: spacemodeling.org/jimz/
I buy some of my parts from several hoony shops in the region, and also from this website: www.erockets.biz/
I also have a fair sized stash of parts: body tubes, nose cone, engine mount parts and centering rings, launch lugs, shock cords, etc.. I've also got materials for.making my own parachutes. Please let me know of you need anything.
As far as stability goes, to me nothing beats the "string test". But do be sure to study up on that topic. Even the best built rockets can be unpredictable.
That's what I've got for now. Good luck and happy flying!

One other thing, by stating the engine you are going to use before the build means you are shooting for a specific weight.  The Estes C6-5 engine is good for rockets weighing from 89 to 47 grams, with no motor.  I usually build my rocket and then figure out what engines can safely fly it.

The simulations say it will reach around 310-ish feet, but i expect it to weigh more( also i might paint it bright yellow)

Bright colors are good for finding the rocket on the ground, darker colors are good for contrast against the sky to help with tracking. Most of us use a combination of both most of the time, for sport rockets at least.

I have figured out that i could put a nc-60 nosecone on it, instead of 3d printing it