You've got it up and running. Cool! I can't say that I care too much for the switch from Intelligence to Wisdom, but I'm willing to admit a large personal bias for Int, so you may take that with as many grains of salt as you wish.
I like int as well, but honestly with the intent of filling the role of primary martial class, int translates into a ton of skill points while wisdom translates to stronger will saves, better spot/listen, and potential synergy with other wisdom based feats (see: The combat focus line of feats which iirc require wisdom. Also Zen Archery, which will make a ranged focused Soulknife really potent). I think the Int focus should be saved for a class that is focused more on skills.

Entry requirements look good, as do the saves and BAB of the class. About the only trouble with the table is that you've labelled it "The Swashbuckler."
What? That's absurd. I have no idea what you are talking about.

I really like this. It's an excellent way to pull attention away from any of your more fragile team members. Or, at the very least, it makes it harder for someone to land a hit if they're bound and determined to focus on someone other than you.
So many people complained the 4e mark was magical mindcontrol... so this class gets it, boosted some, as magical mindcontrol. I thought it was fitting.

I like this direction for the advancement of Psionic Ward. It makes sense and can help a party shore up any deficiencies they might have in their defenses overall. Or, if defenses are acceptable all around, it lets you improve on them. This would be really cool to see in play (And to play). One question though. Is this intended to function at infinite range? As written, there's no limit to how far away a warded ally can be.
Good point. Should probably have a range limitation in there. Thinking either the same 50ft as subversion, or a solid 100ft.

Crystal Mind strikes me as a little odd, as I'd expect a psionic class to grant Power Resistance instead of Spell Resistance. Any particular reason for prioritizing defense from spells, over powers?
I assume (and I'm pretty sure most tables actually using Psionics do as well) Power/Spell transparency. Which means Spell Resistance = Power Resistance and vice verca. I could change it to Power Resistance for the rare group that doesn't do that, but it doesn't make much mechanical difference.

I'm not sure what to say here, other than that I find this feature to be a nice addition to the class. By this point, you've got a refreshing pool of 24 temporary hit points, which you're also providing to one other person, and you can zap people attacking your warded ally. In addition, you're boasting SR of 24, can debuff a significant number of enemies and manifest powers, have pretty good sword-and-board capabilities, and you can now tack on a minute's worth of decent fast healing. This, is fun.
Also in addition to the Empathic Transfer power, the Soulward can take the damage his party members have taken, and then use this ability to clear it. Basically letting him function as a pretty decent out of combat healer. Fast Healing 5 is still pretty marginal in combat, but between combats the Soulward can keep his group going.

What type of action is taken to cause the damage, or is it that an attacker takes damage any time they attack someone that you've warded?
Oops, it was intended to be immediate interrupt.

You might want to specify an upper range for this ability. Psychic Subversion only applies penalties to those within 50ft., but with Psychic Backlash, I could deal at least 7d8 points of damage to someone on the opposite side of the planet, so long as they were attacking someone other than myself. (Perfect crime, here I come.)
Intent was to only be usable on enemies affected by Psychic Subversion. I'll fix that.

Also, is this ability intended to affect non-living and/or mindless creatures? How about creatures immune to mind-affecting effects? I ask because psychic damage is typically invalidated by such conditions.
This was also the intention. Will update.

(Though I do have to ask if someone who's been warded can voluntarily give up this immunity. Immunity to mind-affecting blocks some beneficial things, such as the Good Hope spell.)
I'll add a note that the Soulward can choose to remove those defenses from his wards as a free action on his turn.

The effect wrought by expending your psionic focus is also a nice touch. Protect your ally, deal 20d8 damage to the attacker, and, assuming they aren't dead, they now get to save or find the next 1d4+1 rounds to be quite problematic. The amount of damage you can do with it is kind of frightening (That, or I haven't played enough level 15 characters)
20d8 damage averages to 90. Lots of dice sounds scary, and it is going to be a big chunk of HP, but it is not likely to one-shot any level 15 appropriate challenges. I am worried it may be too strong despite that, but it needs to be strong to incentivise not attacking allies, and to be worth giving up your focus as you note.

I think the 1d4+1 rounds stun may be too much. Maybe just make it a straight up 1 round stun.

Here's a question for you. What happens when you get a couple of these fellows together and they decide to mutually ward each other? Let's say we have three PCs, all with a build of Soulknife 5/Soulward 10. If each person wards the other two, how do the wards interact? Do they stack? If they do, we're looking at each person gaining a pool of 84 temporary hit points (Manifester level of 14, and three wards so, 14 * 2 * 3. A total of 84.), refreshed every round.
Temporary HP typically does not stack unless explicitly stated otherwise. I can make it an explicit statement that multiple wards do not stack. The temporary HP is intended to act as a buffer, not actually stop a level appropriate threat from successfully hurting you at all.

Sentinel Soul [Psionic]
Prerequisites: Psionic Ward class feature, Ward Ally class feature
Your determination to protect the well-being of your allies culminates in your ability to see a greater number of them through danger.

Benefit: You gain the ability to ward an additional ally.
That seems reasonable.

(Note: Should you implement a maximum effective range for Ward Ally, you might have this feat also increase that number.
Maybe. Being able to ward more party members is already a pretty potent effect though. Maybe I could find something else to bundle a range increase with.