Just out of interest - was Princess Alexandra there? I didn't see her in any of the coverage.
I am pretty sure she was sitting next to her brother. A few times we could see The Duke of Gloucester (third row in the second section on the side of the queen; close to the Duke of Sussex) and next to him the Duke of Kent. Princess Alexandra was the next one in that row but only partially visible when the procession entered the quire. Next to her was the Countess Mountbatten of Burma (again, only partially visible for a short moment).
At 35:42 here, when his coffin is being carried into the chapel, there are three men - one two in the back, and one in the front on the same level of pew as the Duchess of Cambridge. They don't look like the Dukes of Kent or Gloucester, so I suppose they're the German relatives?
You are partly right. The Landgrave of Hesse was seated at the front row on the left side (the Queen's side); while the Fürst if Hohenlohe-Langenburg was seated on the front row on the other side (The Prince of Wales's side); with the Hereditary prince of Baden 2 rows behind him. On that same row were seated: Peter (next to Mike and Zara in the previous section - who on their turn were next to Jack/Eugenie and Edo/Beatrice), the Earl of Snowdon, and Lady Sarah and Daniel Chatto (the third 'man' you identified is Daniel Chatto; you can see Sarah's hands next to his, because of her black attire including a hat she is hardly visible otherwise).
To summarize; the seating in the quire was as follows:
Queen's side:
First section - second row: HM The Queen, the Duke of York, the vice-admiral sir Timothy Laurence & the Princess Royal, the Duke of Sussex
Second section - third row: The Duke of Gloucester, the Duke of Kent, Princess Alexandra of Kent, Countess Mountbatten of Burma
Second section - end of first row: The Landgrave of Hesse
Prince of Wales's side:
First section - first row: The Prince of Wales & Duchess of Cornwall, Lady Louise Mountbatten-Windsor & The Countess of Wessex (& Forfar) & Viscount Severn & The Earl of Wessex (& Forfar), the Duke & Duchess of Cambridge
First section - third row: Princess Beatrice & Edo Mapelli Mozzi, Princess Eugenie & Jack Brooksbank, Zara & Mike Tindall
Second section - third row: Peter Phillips, The Earl of Snowdon, Lady Sarah & Daniel Chatto, The Hereditary Prince of Baden
Second section - end of first row: The Fürst of Hohenlohe-Langenburg