First of all, you should never boil your mash before filtering. (1)
Heat water to correct temperature
Add milled grains
Mash for the time needed
Filter and sparge wort
Boil filtered wort
In your case, the best way to filter and sparge would be to use a false bottom, a manifold or a filter screen. If you go BIAB, you need a hoist to lift up your bag and let ...
3.2Ltrs of Strike water & 3.49Litrs of Sparge water appears to be approximately correct for your process. Personally if I were brewing this recipe I might aim for higher volumes closer to 5.4L Strike and 4.4L Sparge, but this is for my own process and boiloff rate. As you can see, the exact volumes depend a lot on your own particular process and the ...