I just recently put a rigid fork on my old MTB with far less thought and calculations then you have put into this with no ill effects. However based on your calculations all looks right. Your existing fork with 63mm travel calculated with a 25% sag would make the axle to crown of your 435.5mm axle to crown fork 419.75mm. The 7mm diffrence in the rigid fork should not significantly change anything. Now the difference between the Offset/rake. In my opinion the 7 mm should not change things significantly. We need to remember all these figures will change with a suspension fork as it goes through it travel.
What you will notice is a much superior feel to your power application and handling, both on and offroad.