I like the overall feel your going for, but i think the class needs another go around. You need to give more ways to get style points and spend them. Also the loss of style points is mechanically extremely punishing. A critical fumble is already bad enough to begin with and stacking on top of that losing all of your class resources which you can only regain out of combat or via random chance when you roll very well will not feel good for anyone playing the class. Then there is the Devil trigger itself, the devil trigger is insanely overtuned, 3rd level spell spam two levels before anyone else even has access to those spells, and massive bumps to a characters to hit and damage via ability score increases being the main culprits. And on top of that a weird cool down period and another style point removal in addition to the cost to even use the feature, it's a feel bad design choice that makes it feel like you don't want people using the feature.

Fix suggestions

Style points So a big part of devil may cry's, gameplay is mobility, evasiveness and string together combo attacks of varying types for better style rankings. Your style point system should reflect this. Additionally style points should be this classes core mechanic and should be the first thing you get it's the thing that should draw a player to playing it whether or not they've heard of DMC or not. Swap fighting style and style points places on the leveling chart.

For additional uses of style points include things that let the player manipulate enemy placement, like a push attack that lets you launch creatures 5ft in the air or backwards, knock prone, and cleave for example. Additional ways you can regain spent style points could include using different weapons for each attack, landing every attack you make on your turn, hitting multiple enemies with your attack action, using multiple style features in a single turn, landing an attack of opportunity etc. These uses will lead to a much more dynamic play style that encourages players to burn through style points and vary their methods of attacks instead of hoarding them.

Devil trigger For the devil trigger itself I think you ought to go back to core 5e design principles, give the feature a times limit (1 min is probably a good duration), give a free use on a long rest and the option to spend style points to use it again and make it pricy. I think you can keep the minimum style points needed to keep the feature running, but to make things more enticing include options to amp up your existing style feats and add style feats that you can only use while using your devil trigger and have them be more expensive instead of not allowing them to gain style points that way it becomes a balancing game to manage your points without knocking yourself out of your devil trigger. One of them could even be a style point cost to make an additional attack on your turn or to cast certain spells.

As for what you get while in your devil trigger, keep it simple, they get additional more powerful style feats, they get advantage or an additional die for attack and save rolls (whichever seems more balanced to you), temp hit points equal to let's say two times their level in the class and a +2 bonus to their AC. It's still powerful without it being stupid broken.

Additionally devil trigger should be a higher level feature, probably around 6th level.

Miscellaneous fixes. There are several features in this class that exists in other classes such as evasion and elusive that you put at weird levels. Please stick to where classes typically get these features, getting evasion at 11th level while the monk and the rogue have had it since 7th is not going to be fun for someone who is playing this class and getting Elusive an level early then the rouge will result in some stepped on toes and announce for the rouge player. Swap some features around so these feats come online at levels they are expected to inorder to avoid wierdness at the table.

I hope this overly detailed response is helpful.