Amumu mana adjustments suggestions

I feel like has high mana costs and while some may argue they are justified, I would gladly give up damage for utility and preserve mana. Since his W is a constant mana drain, and his E a pseudo-spam ability, I feel like having high mana cost on Q & R really hurts him and I'm sure it's because their base damage is really high. It's not uncommon to even go OOM when you want to use your Q+R combo, which atm costs 320 mana at level 18. Spending 120 mana on Q when you miss a target feels really bad and it's not REALLY a reliable escape, you need an enemy or monster. I may even suggest increasing his base mana stat, it's on the low side for his playstyle, needing to use abilities more than auto attacks.

Q: Lower mana cost from 80/90/100/110/120 to 70/75/80/85/90

Lower damage from 80/130/180/230/280 to 70/110/150/190/230

Increase stun duration from flat 1s to scaling 1/1.25/1.5/1.75/2 seconds

R: Lower mana cost from 100/150/200 to 100 at all ranks

Lower damage from 150/250/350 to 150/225/300

Increase entangle duration from flat 2s to 1.5/2.25/3 seconds