As to Ops Manuals, in general these are written for Big Airline operations, and are not practical for corporate operations. SOP's come from The FOM and Company Manuals, and should be practical for the crew to implement, and not just a box ticked.
If you work for a company with an OPS manual written for big airlines then obviously your employer has paid money for that. It is probably because he wants you to do whatever the book says.
Now if they are not appropriate to your operation then why don't you help in offering better ones by getting involved with the guy who is responsible for it ? (Standard's captain or equivalent). If your approach is reasonable, your knowledge adequate, I would be surprised if you weren't getting a few changes through.
Then what I don't understand in your examples is why would your company go to the expense of installing FDMs on board if they don't want you to follow a series of normal operating procedures ?
And if they do want you to follow it ? Why don't you do ?
And if you don't for some valid reason why would your company not be happy with your explanation ?
As for the 160 kts during approach, I am a little bit intrigued. When are you supposed to reduce to that speed ? Most common operation these days, is 160 kts
Minimum til 4 DME often by ATC request, publication in the first pages of the Jepps for that particular airport or due to the low drag technique promoted by airports and operators alike.
Cheers.