Let me tell you about my problems

I play a mage cloth only and right now i am level 13. I've done most of the quests in whiterun and the black star quest for enchanting. My problem is right now im at a level where i cant kill a thing.
My highest skill is Conjuration and alteration cause i always summon and cast mage armor on me. I have the Perk Mage armor that dubbles the effect of your oakflesh or whatever the name is. I have 120 armor with that buff and a flame guy around me plus Sven.
I have destruction but here comes the problem, after i've summoned and buffed my self i have zip mana left to cast destruction so that leaves my skill abit short its only around 30ish and my other two are around 45ish. My conjour and Sven dies in like 2-3 hits and that leaves me saving all my mana to conjour another helper, that leads to less mana for destruction.
In the diffrent tree's i have put perks in Destruction,alteration,conjuration,restoration and enchantment. Mostly the mana reduce perks and regeneration, mage armor and Dual destruction. Gear wise i have a head piece for 12% destruction and a robe that gives 12% Destruction and 75% mana. I also have some enchanted shoes and gloves and jewelry with diffrent resistens gear.
So to my questions.
1. Any tips to help me still play on this difficulty would be nice.
2. I think its hard because of my low destruction skill compare to my level but should i use my other skills less and try to survive with just destruction?
3. Do i really need to level my enchantment to 100 before i can play mage this way on this difficulty?
4. What is the strongest type of character to play on master difficulty?
5. Should i try to find a new companion and let him do more of the fighting?
6. Have i spread my self to thin in the diffrent trees making me weak this way?
7. Right now i cant enchant more destruction on more gear since it only fits on a few pieces.
Thanks all and btw i dont wish to lower the difficulty and im sorry for the bad spelling.
