Sounds all good! My complaint about TSD is it is lacking a great many of the techniques we both know, it seems to be a simplified (a childs version even) version of karate. There is no 'crescent step' as you call it at all, and far fewer techniques. I wish I had been able to stay with Wado with it's depth, I know TSd people will now all hate me but I can't help it. Plus TSD is claimed to have been going for a thousand years in Korea.
I like Wados ( and yours) versatility,TSD doesn't even seem to have an elbow attack ( according to the books I have and have been taught) even though it's in the patterns. I shouldn't moan I suppose about the style I do but it's frustrating. Luckily though we don't belong to any organisation now so I will teach all and any techniques that are useful and some of our students will go on to Wado and Shotokan schools in the future. It keeps me going on my Wado, my instructor has a good friend who is also a Wado 5th Dan who comes along every so often to keep me right. Our katas now have taken on a more Shotokan/Wado feel too. We haven't changed the moves just do them with more 'beef' you could call it I suppose.
My instructor is very fond of two knuckle punches, when he punches in fact he always has two knuckles higher, thats not just in the class, he uses them 'outside' lol. We kick with the shin too but that comes from Muay Thai rather than karate, in Wado we use all the kicking surfaces you mention. We don't snap our kicks, other than front snap kick lol we do them 'heavy' (and this is where I can't explain things well again), do you know heavy hands? If so it's like that, still fast but they come in heavy and stop on target for a couple of seconds then back. It feels like a mule kicked. I've heard it described as kinetic kicking but have no idea what it means lol. I do know it hurts... alot!
The TKD guys we have in our class have speed, flexibility, and a lot of very fast high kicks; I have to say they're impressive. I honestly do not have the background or experience to say anything negative about TKD, TSD, etc.
I started training in Wado in Lakewood, Colorado back in the late 1980's, but I only did it for a couple months; didn't earn any belts. I don't recall any of it, unfortunately, except the cat stance (which we don't use) and the horse stance, which is similar to our seuchin dachi, but deeper than ours.
We do practice a kick such as you mention, but it's not part of Isshin-Ryu as I understand it. Sensei calls it 'dead-leg' and for example, we'll do a roundhouse type kick and really lay the leg down on the bag (we can't really kick each other with this kick, it's way too strong). It's like swinging an ax into a tree, it really sinks in. You can feel the power behind it. However, the argument is that it's a risk; if it doesn't disable, it can be caught or trapped.
With our vertical punch, the wrist is held straight so that the back of the hand is level with the arm. The thumb goes on top of the fist, which is unusual for Okinawan-style karate. It rests on the second knuckle of the index finger. The fist is angled downwards, but only slightly; I've seen Youtube video of Isshin-Ryu practitioners that angles the fist down way too much. The goal is that the top two knuckles will impact the opponent. Our 'vertical fist' isn't truly vertical; it's canted a tiny bit, so it's more like 10 o'clock if you know what I mean. We do not use a torquing punch except in Sanchin, which we do Goju-Ryu style (we also have a vertical punch Isshin-Ryu version of Sanchin).
When I mentioned the shinbone kick, yes, that's also not Isshin-Ryu; I think we got it from Muay Thai like you.
Our blocks differ from Shotokan a bit. We block with the 'meaty' part of the arm on jodan type blocks. For example, our exercise 'jodan uke, seiken tsuki' is a head block followed by a reverse punch. The block consists of stepping forward (or back as necessary), and blocking with the arm over the leading leg. The arm crosses the center line and then rises with force, with the hand in a fist and the palm facing inwards towards the face of the person throwing it. In other words, we can see the inside of our own hand, not the back of our own hand. The elbow comes up to about eye-high. We don't lean into the block, we wait for the punch to come to us. We also practice 'rooting' ourselves into the block so that the power of the opponent's punch isn't being absorbed by our arms.
I've tried blocking the other way, and it really hurts when the person's fist or arm comes crashing down on your arm. I like the 'meat' block better! We also have an upper body block with the open hand which can be either a chop block or it can be turned into a deflect-and-grab, which is sweet. Throw the open hand up, turning the hand from inside to outside as it rises, deflect the incoming arm upwards, continue to turn the hand, grab the arm, and pull it down hard to the obi, while launching the fist from the opposite side. By turning their power into your own rotational power, they are actually fueling the power in your punch while at the same time you're pulling their face do to meet your punch; fantastic!
I would love to get together with practitioners of other styles sometimes to just compare and spar a bit and practice different things and see what works and what doesn't (for me, I realize some people are better suited to different styles). Fortunately, my dojo doesn't claim to be the one true karate, etc. We do Isshin-Ryu and we like it, but we see other styles as full of good stuff too.