Texas Method Squat Stall after 420x5

Background: 17 yr old male, 212 lbs, 5'11", gaining 1 lb per week on Texas Method.
Squat: 420x5x1 ID, 375x5x4 VD
Bench: 247.5x5x5, no issues
Deadlift: 475x5x1, 410x5x3, no issues (VD on Mondays in lieu of power cleans; I plan on competing in powerlifting)
I have been running TM for 11 weeks now while gaining weight, about a lb per week, since I began the program. I started off with a squat intensity day of 380x5x1 and a volume day of 335x5x5. 5 weeks ago, I just felt beat to hell and had a real grind with 405x5x1, so I dropped the 5th volume set. Hitting the intensity day set was considerably easier the weeks after doing this. Last week Friday, I hit a 380x5x4 volume day and failed the 5th rep of an attempted 425x5x1; when I reviewed the film, I realized that my form crept and I had knee slide due to my toes not being pointed out enough and subsequently I didn't keep my knees out enough. I fixed this error on my VD set this week of 380x5x4, which was somewhat of a grind and, in retrospect, it seems that my VD is now too high. During this whole time I kept my VD right around 90% of my ID, which this current VD is still. Now on this week's ID with correct form, I only hit 425 for 3 reps.
I think that it is important to consider that I did not feel beat to hell by my volume day this week, although it was hard--probably harder than it should have been.
Should I drop a set or drop weight on the bar while maintaining the 5RM on Fridays, or should I keep the same VD but switch to 2 sets of triples on ID? Or should I perform some combination these potential solutions?

Thanks,
Jack Morrison

Your comment on power cleans and powerlifting makes zero sense. I've seen the ridiculous number of form checks you've posted for deadlifts, so it might take you awhile to get the power clean down, but given your numbers you are probably a good candidate for them and should definitely learn the movement.

As far as the squats go -- I have a unique suggestion. Just do the ID on both days. You seem to respond well to training, it might work, for a little while at least. That's what I've always done. Besides -- who wants to squat 5x5 or 4x5, that's a bad time.

You started your SQ ID with 380 for 5 and kept going up each week to 425 for 5? That's like 10 weeks of doing 5s for ID. Your youngness gave you a great run, but you need to give yourself a break and cycle through the lesser rep ranges for ID.

Cycling through rep ranges makes sense. Do you think that my VD weight at 380x5x4 is too high at 90% of ID at this point considering that it felt particularly hard, but I didn't feel beat to hell afterward?
P.S. Thank you so much for being patient with me on my correcting my deadlift form. It seems that I have finally got it down consistently; I am at 475x5x1 thanks to your help and with any luck I should hit 500x5x1 pretty soon. I really appreciate it.

It's going to be a bit tricky to know if the VD is too heavy now as you likely have some ID fatigue spill over. A volume day at 90% of ID is fairly high, so it might be good to deload for a week now and then start up again with a slightly lower VD.