Will: So that deck looks a little different from the one on Channelfireball, a little less burn focused but more capable of countering things and adapting. Looks more interesting and fun to play, plus you have a lot of the necessary cards already!
My overall thoughts are-I would suggest shaving the hallowed fountain, temple of triumph, and the Kylar- as far as I can tell she’s the only real white card in your 75, which isn’t worth distorting your manabase over(especially with playing 4 wizard retort).  Dovins veto could be easily replaced by negate, and Kykar is probably actually worse than a Kefnet eternal. You may also want to replace infuriate with Samuts sprint, I think scry is worth a little more than 1 damage, but it’s close. Also, spell pierce is a very good counter, even maindeck- it’s just so cheap.
So as for your other questions-
1. Pretty damn important, he runs away with games and enables spells. However you could m use a burning prophet or two. augur is another good 2 drop, but he doesn’t attack well. Maybe wait until Feaher isn’t as big in the meta, and the price will go down.
2.yea, 24 lands for a deck with nothing over 4 mana and a lot of controls is a little high. You could run 23 or maybe even 22, but you may want to use some number of Samuts sprint(and burning prophet?) in addition to Opt to scry into lands if you need them.
3. I don’t think one copy of Kykar is worth adding the third color here
4. Our local meta is largely Aggro, and this deck is designed to beat field of the dead, so you need some heavy anti Aggro(flame sweep). Tibalt is good against Vamps. You probably also want some spell pierce/negate in there. Role reversal is good against rock too. Flame sweep is at its best in this deck, because your fliers survive it and your 1/3 wizards do too. If mono red really takes your lunch, you could try a wall of runes or electrostatic field, because they can’t burn it out easily
Kasmina and maybe Saheeli should be good against control(or our boy Murmuring Mystic, also a wizard!). But IRL, Kefnet is probably the best card against control, and could probably replace the Kykar maindeck.

https://www.mtggoldfish.com/deck/2017612#online
https://www.channelfireball.com/articles/updating-standard-izzet-wizards-with-lightning-stormkin/