With the build you’re going, you’ll likely not run into any mana issues. I’d just not put any points into SPR at all. Mana potions will cover you the whole way.
As a note, even with attributes, the cryo skills don’t seem to scale too well ( for just taking 1 rank in cryo, you’d need more ranks ). However, the pyromancer skill Flame Ground scales extremely well, so if you were going to take 1 DPS class at rank 2, I’d suggest that. ( I made a cryo 3, and the skills only kept up as I levelled them up, but I took pyro rank 1 after, and flame ground lv5 did more sustained DPS than any skill I had ).
The one weakness that flame ground has it that it doesn’t effect flying monsters, but you can work with it since you’re taking linker, and just link a ground mob to those flying mobs.
About SP Potions: They do not scale, I think this should change. It would make taking points in SPR actually worthwhile, if your SP potions restored more.
Also, as far as pures being bad, not so sure about that. They’ve made a patch a while back to mitigate this, giving a 10% bonus to your STR/INT stats, so the more you pump into INT the more you’ll get out of that.
So, tldr; I suggest taking your 2nd rank in Pyro ( flame ground, and fire enchant for support ) and going INT / CON. The distribution is up to you, I went 4:1 INT:CON and was comfortable with the damage/HP I had.