I have some questions about skyrim and dragonborn that maybe someone can answer for me.

1. Did installing dragonborn dlc automatically make the rest of the game (skyrim) harder? I started a game over after installing dragonborn and I seem to be having a difficult time playing the vanilla game. I haven't changed the difficulty level. For instance, at 12th level I was in a dwarven ruin when a dwemer machine boss (one of those gargantuan dwemer machanations) appeared and attacked. I had to use everything at my disposal just to barely survive the encounter. That included lydia, a frost atronarch, and me with full set of steel armor and dual bound sword attacks. That dwemer machine could nearly one shot me, and I just BARELY survived. I can't recall ever having any trouble at all with those things.

2. After installing the expansion, I noticed lydia had different voice dialogs. In particular, I noticed she sometimes had a different response to asking her to share inventory. Has bethesda redone follower AI in any significant way? Does anyone know if Illia (the ice mage at darklight tower) is still broke? Just how much has dragonborn changed vanilla?

3. General skyrim question. Can enchantments bring skills above 100 in a useful way? For example, can fortify heavy armor enchantments bring your skill beyond 100 and actually make your armor better than it would be if your skill was 100?

Any help appreciated.

1/ I dont think so. I remember the first one I faced was hard , but I let lydia charge on in and hit it from behind. Its often about how you go about it. I used that approach after it first one shot killed me the first time. However, I didn't have dragonborn loaded at that stage.
2/ Lydias dialogue changes after some level ? . I remember been grateful her responses weren't sarcastic to sharing inventory. Didnt have dragonborn then either.
3/ dont know, never bothered getting enchantment very high.
Hope yu have fun in Dragonborn. Theres some good armour in there.