Indeed, different things do work for different people.
First of all, don't become discouraged at your groups, when I started pistol shooting just over a year ago my groups were atrocious at best
A guy at the range said he would help me out and in fact most of what he taught me is repeated in that Jarrett video above - stance, grip, tip of finger on trigger pad & squeezing, sight picture. Watch it a few times and note down the points he makes.
It's a LOT to take in so I spent countless hours addressing one aspect of the above and focusing primarily on that every trip to the range, I found it better to take it one step at a time...while evidently being conscious of the other aspects.
Most difficult part for me was learning how to hold the pistol correctly in the web of my hand, it wasn't natural to me and took time to erase that tendency I had, difficult to explains but it's in 38-1.04 of the video.
learn with your .22lr and tighten up the groups before shooting the .380 - you can practice and hone your skills with thousands of rounds for next to nothing as ammo is so cheap and it's all transferable to bigger calibres - in some ways I'm glad here(Luxembourg) we have to do 1 year of 22lr pistol before moving up to centerfire.
I'd also recommend shooting strings of 5 or 10 rounds before looking at your spotting scope(guessing you're shooting at 25m ? ). I found shooting one round and looking at the spotting scope is counterproductive.
I also found it difficult to have a blurry target and focus solely on the sights.
On a standard 25m target my average 10 shots would be 3-4 in the 10 and the rest in the 9 area - occasionally I have 1/2 shots in the 8....but that's after hundreds of hours, thousands upon thousands of rounds downrange.
I've spent much of the past 6-9 months shooting pistols to the detriment of my rifle shooting but it is incredibly rewarding when you get it right and see the improvement.
like most sports, get the basics down and then practice,practice, practice
as for the glock trigger....well a friend hates his glock/doesn't want to sell it but wants to keep one in his collection. As I was restricted to 22 for 12 months he said I could reload and shoot his til I get my own 9mm. I wasn't a fan of it but it has grown on me a lot. It's not a competition pistol afterall.
To sum it all up - don't be discouraged, try to address one aspect at a time on every trip to the range - obviously incorporating the other aspects but really focusing on perfecting one and practice as much as you can.
I'm glad I learnt how to shoot with proper technique before moving to 9mm but I got a LOT of hassle from guys at my club shooting a S&W 41 with two hands