Is this homebrew Far Realms domain balanced compared to the official domains?

I am making a compendium of homebrew Cleric subclasses, spells and feats, but I want to make sure it is actually balanced and there are no glaring loopholes or broken combos with existing feats, spells, and subclasses before I release it. Is this homebrew Far Realms Domain balanced compared to the other cleric subclasses?

Far Realm Domain

You worship the creatures that dwell in the infinite abyss beyond the outer planes, that most creatures cannot even comprehend. Gods of the Far Realms include Cthulu and Tharizdun.

Domain Spells

Level
1st Arms of Hadar, Cause Fear
3rd Magic Mouth (R), Mind Whip
5th Clairvoyance, Hunger of Hadar
7th Black Tentacles, Summon Aberration
9th Antilife Shell, Contact other Plane

Bonus Proficiencies

You gain proficiency in Intelligence saving throws and Deep Speech.

Aberration Lesser Boon

You gain one of the following abilities of your choice:

  • As an action, you can turn your arms into tentacles, increasing your reach by 5 feet. For the purposes of grabbing objects, your reach increases by 20 feet, though you cannot attack or cast touch range spells in this range. You can transform them back into normal arms as an action.

  • As an action, you become slimy, slippery, and rubbery. This gives you advantage on checks to escape from grapples and restraints, and allows you to fit through spaces only 6 inches across. You can transform to solid, dry form as a bonus action.

  • You always know if your mind is being read. You can use your reaction to do 1d12 psychic damage per level you have to whoever is reading your mind, unless they succeed on an Intelligence saving throw.

Channel Divinity: Greater Arms of Hadar

At 2nd level, when you cast arms of hadar, you can use your channel divinity to increase the effect. When you do so, all creatures who failed their saving throw are stunned until the end of their next turn, in addition to the spell’s normal effects.

Channel Divinity: Gibbering Mouther

At 6th level, as an action when you are grappling a creature or being grappled, you can use your channel divinity to grow mouths across your entire skin. The other creature takes 4d4 piercing damage and stops grabbling you if you are the one being grappled. It becomes frightened for 1 minute. The creature can make a wisdom saving throw at the end of each of its turns to stop being frightened.

Potent Spellcasting

Starting at 8th level, you add your Wisdom modifier to the damage you deal with any cleric cantrip.

True Form

At 17th level, when you are reduced to zero hitpoints, you can choose to briefly reveal the true form of an aberration. All creatures who can see you must make a dexterity saving throw to avert their eyes. On a failed save, they are frightened for one minute. At the end each of their turns, they can make a wisdom saving throw to stop being frightened. In addition, you regain 1 hitpoint. You can use this feature only once per long rest.