Freeze Boost is a waste of points (same with all the similar skills for the other elements). How it works is it's multiplicative. So if a spell has a 20% freeze chance, 10% of that is 2%, for a total of 22% chance to freeze. So not worth the 10 points. Avoid these at all costs.
I've never used Deep Freeze, but basically when you freeze something the freeze effect will eventually break if the enemy takes enough damage. The skill just increases that damage threshold by 600%, so it will take more damage before it is broken free. You could probably take this if you want to focus on ice, it'll just make your freeze way more effective.
Freeze Detonation (Freeze Ignition) is bad, don't take this. It doesn't do enough damage and the cooldown is too long to be useful.
Also, it's not a good idea to focus purely on one element because once you're higher level you'll get what's called "Fused Techniques" or "Compound Techniques". These deal 2 types of element damage, and do a HUGE amount of damage. They also benefit from both of the masteries for their elements. So Fire/Dark, Ice/Light, Wind/Lightning.
I would suggest something like this. You'll still have maxed out Ice skills, but you'll also have pretty good multipliers for Fire and Lightning, along with maxed out Wind/Light/Dark on the Techer tree. This build will also benefit you if you want to swap elements due to the enemies elemental weakness, or if you're in a fight such as Profound Darkness or the mini-boss in ultimate and it ends up resisting ice.
(this is a lvl 80 build for the new level cap)
Note: If you want to use a Talis instead of rods, make sure you swap out Rod Shoot for the 2 Talis skills. Put the 3rd extra point into Lightning mastery or something. Also, I've taken Tech Charge JA addition on the Techer subtree. You need this skill, but it's only required on either Fo or Te tree, not both.
Also, fire techs are pretty mush useless without Flame Tech Short Charge. The points there are purely to boost the Fire/Dark compound tech. Lightning is better than Fire, so as a secondary element to focus on you're better off putting spare points there than in Fire. Plus the PP save on Lightning techs is useful even just for Ilzonde, which is your movement tech.
Edit: if you're really not bothered about boosting the Fire/Dark and Wind/Lightning compound techs, you could drop all of the points from Fire, and some of the points from Lightning (I recommend still keeping Lightning PP save just for Ilzonde). Those spare points I guess you could put into Photon Flare, but I've never really been a fan of that skill cos it's only about a 5% damage increase for 20-odd skill points.