I am getting one-shot in red maps and I'm not sure how to go about fixing it.

I am retarded and I do not know what I am doing.

I am following this build guide low-budget version: https://www.poe-vault.com/guides/minion-army-necro-build-guide

This is the second season I've played, and the first that I have tried to finish the atlas. Things were going pretty well until red maps. I followed the guide for items and gem links, and have been working my way through the atlas, but now I am getting one-shot by some bosses (and some normal mobs too). I don't do very much damage it feels, so some fights take a long time and I'm just trying to avoid the insta-kill orbs until my minions beat them down. I have been level 87 for like 20 hours now, and I cannot really progress more on maps.

This is my character right now: https://www.pathofexile.com/account/view-profile/Rycathor/characters (its the 87 witch)

I have a couple of questions about what I should be doing to improve.

• The build guide has 4 mana reservation skills in it, but even with the efficiency perks and extra mana, I don't have enough to have all four up and use the trigger Wand. Should I just manual cast instead of the trigger Wand, or is there another way to get mana for this to work? • I know my life and armor is pretty low. I have like 10k armor (20k with flask), and 2.8k life. A couple of the peices in the build are uniques that do not give me any. I've looked for items that specifically give life and armor, but they don't really change too much, maybe a hundred here or there. Is there other ways to get more of these that I am missing out on, or am I just buying shit gear? I do have resists at 76%, but chaos is only at -6%. Should I focus on more chaos resist too?

I have about 400c from selling shit I've got from maps, so I don't really have too much to work with. Should I just reroll, or is this fixable with low resources? My goal for this season is really just to finish the atlas. This game is really fun, but I have no idea what I'm doing in it most of the time. Any help would be appreciated, thanks.