Nitromors will not damage the plastic diamond in the grip gap unless left sittiing on it for extended period. I have used it on several BSA and Parker-hale stocks with these white plastic bits with no ill effect.
Now as to your scope I would not put those horrid looking Sportsmatch things on such a classic rifle. As for the Nikko Sterling 4x32 yes I do believe it an the old Special Sporting and Special 4x32's were good scopes. It's only in modern times are our eyes so poor that we require 6x minimum magnification to shoot deer on the oepn hill. The 4x32 does give up a bit of light transmission in the gloom especially woodland but that was the std size some 40 years ago. I would ahte to hazzard a guess at the number of deer such scopes have grassed over the decades. One must remmber that using a scope was considered cheating in Highland stalking only 60 years ago by many.
As for scope mounts I see the scope you have uses a 1" tube even though the makers site says 25mm
It make me wonder if they don't know that 1" is 25.4mm how good is their QC? .................................... anyway a set of P-h RAHS3 rings would fit teh scope onto your rifle and are about the easiest size to come by here is my Majestic featherweight fitted with a Lisenfeld 3-9x44 held by a set of P-H RAHS4 rings (26mm)
Ahhh just noticed in the photo the mount is a one piece P-H #26 that I used before finding the RAHS4 rings... whoops! and since then I have adapted a set of steel Hilver Brno mounts and fitted those:-
Not the best photos I'll agree but the scopes objective clears the rear sight as it's not long enough to reach it but as you see the rear sight is easily drifted out of it's dovetailed slot and filed away safely for re-fitting at a leter date should you so wish..
There is still some Steel Hilver rings to fit the P-H bases available new but they do require the hole drilled in the base of one and the supplied recoil stud pin pressed intot eh hole. Why they didn't fit them???.
Another option which will not cost a firtune and allows a huge range of rings choice is the Weaver type bases which come is alloy or steel and would be far preferable to that dreaded Sportsmatch air rifle mount.
However it's your rifle so your choice
.
Now to the touchy subject of floated barrels....................................... NO your BSA does not have one, never did have one, a and will likely shoot very well without you messing with the the stocking up of the rifle. If your going to use a bi-pod then not only will you have to swop the sling loops for studs but you need to get the machine screw front stud and ferrule or it's going to eventually tear out of the wood. the studs are short on these due to the design of the forestock the 1st Pattern Monarch I acquired has this problem which the selled failed to mention I fitted a sling and the rifle nearly hit the ground when the sling loop pulled free under the rifle weight. It was tripped by over tightenign or Bi-pod use in my opinion. I am looking for a suitable machine screw and ferrule sling loop to repair it with.
Personally I would not be having such a rifle adulterated with screwcutting
however it's got to be you choice.
The bolt handles were I believe were blacked, but saying that the later CF2's were offered in the white on some and blacked on others so it could have been either. I do not have a 2nd Pattern Monarch to go by however the one shown in John Knibbs BSA book has a blacked handle.
I would polish it with 600 wet and dry then get soem 1200 and finally metal polish then you can decide to either leave it bright of blacken it. Here is the polished bolt handle on the 1st pattern Monarch we have just re-furbished as a .280 AI:-
There are some cold bluing creams or solutions available and if done correctly then look good but will not wear as well as rust bluing ot hot salt blacking of course but one can always touch up the cold bluing one self. Note the one piece #16 again but it does not quite fit the long action properly so once again after trying it a set of the correct 26mm rings were fitted the the Kaps scope.