Is my homebrew Subclass balanced?
so I don't exactly have much experience in balancing considering I started playing it not too long ago but I want your opinions on my homebrew Subclass and ways I could balance it because I really don't want to be that guy at the table who creates a op character and disturbs the progression and overall campaign. Anyways here's my subclass it's a subclass of fighter called duelist and it excels in singular fights and has high dex for general movement it's signature ability is "Duello" which is used for activating a duel between you and your enemy where you charge an enemy and then clash then both get staggered a little (this is all scripted and the animation? idk what to call it changes based on enemy) and then the enemy and you are put in a duel which is a state where the character gets increased stats and some advantages that scale linearly based on how long the duel goes on for firstly you get a flat +4 to attack rolls and gain even higher movement speed and then the buffs that scale linearly so first off you get +1 AC every turn the duel goes on for and the hard cap of AC is 35 and nothing can extend it beyond that so let's say you have a flat 15 AC normally it would take 20 full turns for you to reach it . in this state you can also target specific body parts of the creature you're fighting to give it debuffs but this takes a turn and does little damage only debuffs (this works less effectively against bigger enemies for example you would need to strike a hill giant many times on the same body part to apply the debuff) the specific debuffs are still not decided but the debuff system is final and will exist that's all the good things now onto the bad things this class is fragile but not that fragile it can withstand s few attacks but caution is still needed .in brawls my character has the direct disadvantages namely -2 to attack rolls , dealing only 4/5 of the damage they would normally (rounded up) and having -3 to AC . that isn't the end though as if I am hit by a third party in a duel the duel state immediately cancels which prioritises me to not call duels near groups of enemies. a few misc things I'm including I wanted myself to have options to isolate enemies so I have some manuevers to do so since I am incapable of using (I would've loved spells like blur and misty step) the specific manuevers are (I can only do one per 3 turns) feinting step which allows me to feint enemy attacks and attack after for example I move towards an enemy and feint . if they attacked I get to attack them with advantage on the damage and if they held then I just wasted my time and then proceed to attack normally , next one dash which is self explanatory and can be used as a bonus action after attacking or dashing in to attack) and third one which is my only crowd control option whirlwind in which is spin with my two swords and then disengage backwards now all the things I mentioned before were level 3 abilities instead of the weak point debuff which is level 7 now on 10th level I gain the ability "Momentum" on every turn during a duel where I am not hit I gain a +1 to my damage rolls as true damage and it caps at 5 , at level 15 I gain "execution" if I have all the body parts of an enemy debuffed and I also have the max cap of momentum i mentioned before I can perform a devastating flurry of attacks which heavily damages the enemy (this ability has a cooldown of 10 turns) , at level 18 I gain an ability which I don't have a name for but I gain +3 to save throws by enemy abilities if I am in the duel state against them , i am not great at naming things am I? anyways let me know what you guys think and what tweaks I should make