Hi Max
No worries. Glad you are finding it helpful. There is a lot in some of your points. Firstly, to the contour question, as that is relatively easy (short answer - more is better).
I believe you benefit from the heaviest contour that you can find to fit within your weight constraints. Quite simply, the less material you remove, the better off you will be. The only counter-point to this is staying within your weight limit. So for accuracy and all round shootability, I would rate a #7 contour over a #6, but better again would be a #8 over a #7. Likewise, if you needed to cut a barrel, I would rather cut the muzzle than the chamber end (retain the heavier, stiffer section over the lighter section).
I defy anyone to prove a theory that a given contour or barrel length is going to give you an advantage. A number have come forward with hypothesis, but none have been proven. For example in the early to mid 2000s, Bill Calfee (who is a very fine rimfire BR rifle smith) advocated a process of "ringing" a barrel to determine the best point to cut the muzzle and install a tuner so as to minimise any negative harmonics. This was debated on a number of accuracy forums for a some years. But when several very good BR gunsmiths tried Calfee's approach, they could never replicate the results Calfee claimed. There are plenty of theories out there, but the results in the winners circle are the only meaningful measure in my opinion (I have beaten people in competition, and then they explain to me why in theory they have better equipment than me!).
Regarding benchrest, I would very strongly advise you to find local matches and go visit them. You will learn a lot and it will really help you decide what you want in terms of a discipline to shoot, and also the equipment you want to invest in. I believe too many beginners wait to attend a match eg "I am not ready to compete yet so I will practice for a month/year". This does them a real dissservice because they can learn any umber of bad habits on their own, and miss out on the really rich learning experience that comes with competition. Far better to get to a match early, have an open mind, and absorb the information that will come from very experienced competitors.
Also, a lot of people that are new to the sport will invest in equipment (sometimes at considerable cost) that is not as well sited to competition as they had hoped. If you get in there with nothing, and see what successful competitors are actually using, you will be far better placed than doing research at arms length.
I can tell you how much good stuff I have learned from competition. It REALLY helps all the other shooting I do.
Benchrest comes in a number of flavors, but I will limit this to two primary categories. What is often referred to as "short range" BR, and is generally shot at 100 & 200 yards, with very limited matches at 300 yards, has light class (10.5 pound rifle) and heavy class (13.5 pond rifle). These classes have limits on barrel contours (amongst many other rules) that would limit the use of what you are currently building, and the caliber choice would also work against you (IE you will not be at all competitive).
Perhaps a better option based on what you ave mentioned would be 600 yard BR. This has a light class which permits rifles up to 17 pounds, then a heavy class which goes from >17 pounds to unlimited weight. You will see the vast majority of competitors using light rifles at these events.
Another alternative given some of what you have mentioned may be F Class open, which is shot from a rear bag and front rest, has a maximum weight rifle of 22 pounds, and is shot a one hundred yard increments from 300 yards to 1000 yards (and sometimes out to 1200 yards) from prone.
I would encourage you to attend some matches, talk to some competitors, and see what looks lie your "thing". I am sure you will get a lot out of competition shooting if you put some effort (and unfortunately $$$) into it.
