De Ligt was excellent, he dominated Gyokeres and marshaled the back line really well, and Yoro is constantly improving, he's our best CB on the ball. We absolutely need a keeper and a midfielder before the window shuts. Like you say, there's plenty of solid keepers that would be an upgrade on the 2 calamity Jane's we currently have. I'd love us to have gotten Baleba but there are options like Elliot Anderson and Mateus Fernandes, or perhaps Stiller from Stuttgart or Larsson from Frankfurt.
Forgot to mention Yoro, for a 19 year old, he looks extremely promising. You can see why Lille wanted to keep him & a host of European clubs wanted him, has a lot of potential.
That's another sort of tactical thing I'd mention, I don't think de Ligt & Maguire should feature in a back 3, as those 2 wider CB's are require to almost be like half CB half FB at times. You need defenders with a bit more agility & mobility playing in those wide spots. de Ligt & Maguire should be competing for the central role. Yoro, Martinez, Mazraoui, Shaw & Heaven should be competing for the 2 wider roles.
I wouldn't even think about it, we know Middlesbrough will accept £20m for Hackney which in today's market I think is very reasonable. It's a punt as he's never played at PL level, however he does have 3 or 4 years of Championship experience so he's been well moulded to play in a physical league.
Even if we sign him & it becomes apparent after a season or two that he's not quite up to playing in the upper echelon of the PL, where we aspire to be, I don't think we'd have any problems recouping some or all of the money invested like we did with Dan James who like him or not, was actually pretty solid in comparison to some of our other high profile signings that followed/replaced him.
I'd then try to save our pennies & try to target Baleba or other midfield targets next summer, presumably when Casemiro leaves on a free unless we for some unknown reason pick up his option for another year.
Goalkeeper wise, honestly we don't need to strike gold & find THE guy to be our goalkeeper for the next 10 years, there's bound to be somebody. The most glaring option would be Donnarumma given his PSG omission, perhaps on a loan deal with option to buy at the end of the season & see what happens.