I'm somewhat busy working on hw throughout the night, but I'll be watching through this intermittently and will edit with comments in a little while, nice that you finally got to record something; I think I can give some relevant advice, but maybe not super specific things, hopefully some experienced Ness players will comment eventually ^^
EDIT: Here are a couple of things I noticed:
- Can you wavedash OoS? I didn't really see you do it at all, but it's pretty helpful for things such as getting grabs in the earlygame which can lead to vital combos, especially against spacies. It's also very important for Ness in certain other matchups like Marth, as it gives you a way to start something and punish, or another potential option to get out of your shield and away in the case of imperfect shield pressure or something. Since Ness doesn't have the best OoS options in general (Nair is good though, and maybe Bair to punish a laggy hit on shield), it's pretty key I think, and something I'm trying to work on myself.
- You seem to roll a lot (for instance, something like 3 times in a row at one point vs Fox?). Sometimes there isn't too much more you can do to get out of shield pressure or otherwise but try and buffer a roll, but Ness' roll is quite slow, so try not to overuse it. You seem to mostly do this OoS, and get stuck in shield fairly often, from what I could see.
- Work on elongating your combos and converting hits better; I know this can be tough against floaties, but it's really important to get as much as possible out of every grab or hit you get, especially against spacies. In particular, try to go for more Uthrow > Uair > Regrab/Uair chains vs Fox, ideally ending in a Bair or platform techchase or something, rather than just doing Uthrow > Regrab > Uthrow stuff (I feel like that could be DI'd out of or acted out of with shine or something except maybe at like 0%, also....is three of those really a true combo?). Basically moar Uair, against spacies, falcon, weight classes like that at least.
- Try to stay mobile via wavedash > dashdance and vice versa, and get as much distance out of Ness' WD as possible when desirable. You do this pretty well sometimes, but it's often just when they're dead or far away, so try to space and punish with this more I guess.
- As you mentioned, you could also work on platform game a bit, both in terms of movement and platform techchasing. I like to try and edgecancel stuff pretty often, but I guess that isn't quite as essential, and not always the best option.
- Your edgeguarding is fairly good, but you miss the bat sometimes, and there are also instances where it would be good to go for another edgeguard, and you should mix up your edgeguards a little bit in general. Dtilt is great against falcon/ganondorf and spacies coming from below, bat is good against spacies in most cases as you obviously know, pk fire situationally depending on the character and such, and Dair is also good for stylin'/disrespect xD. Something I like to do as well, especially for characters with punishable recoveries (I wouldn't try it on Marth, G&W, etc.) like the spacies and Falcon, is to just edgeguard with fair if they aren't coming from below. It can reset the situation at mid percents, and potentially just send them far enough away to die or only have the option to take ledge at higher percents (then you grab it of course lol), so if you're in doubt of whether they're going to go for a ledge sweetspot. or recover high or into your face, I think Fair can be a decent option.
That's mostly what I noticed as I watched, as far as things to work on go -- sorry for the wall of text, but hopefully some stuff I pointed out will help you out! You did some nice combos and stuff at certain times, and you seem to be pretty good at walling out your opponent with Fairs and such in the neutral game, although your neutral game does still has some room for improvement since you end up in shield often from what I could see. You did a good job of chaining Fairs against the lighter characters like Peach, and punishing with Bair (don't be afraid to punish missed/shielded Dsmashes with that either, you did a few times I think but others you ended up just sitting there after or only Fairing OoS). Thanks for the upload, it's nice to see some new vids on here (though I wish there were way moreeee ;__; ), and watching helped me think about improvement for my own play too ^^