Alright, first off, there is way too much wood below the ramrod. Make it 1/8" of wood (MAX) all the way from the entry pipe to the breech (and continue this new line on through to the butt). Making it a quarter inch thick there will result in a very thick, fat gun. I know, I've made more than my share of thick, fat looking guns.
Your "web" dimension is fine. It would be too thick for a heavier barrel, but for this one, it's like you're pretending your barrel breech is wider.
If your trigger is where it needs to be in relation to the butt/comb/wrist, then that is your starting point. Locate the desired position of the sear in relation to the trigger (I always put the sear bar 1/2" from the trigger pin. Many people today put it much closer.. which is fine if you want a really LOOOONG let off. Many old guns are at least 1/2" and often farther... but I digress). That gets your lock position, fore and aft. Now, up and down. It is perfectly acceptable to put the lock above the centerline of the barrel. In fact, with such a small barrel, it is almost a necessity. It was often done 200+ years ago, so it is not unusual at all. This will get the nose of the lockplate up a bit, and closer to centered on the "web" of wood for your front lock bolt. You can also tip up the nose of the lockplate a bit. I don't like doing that, myself, but English locks of this vintage do tend to have narrow front ends and often display a bit of a tipped-up attitude anyway. Again, I think the position you have shown for the flat faced "Early Ketland" lock is pretty good. It looks slightly above center and tipped up just a hair. Also, because the lock bolt may still nick the rod hole, you can notch the front lock bolt for clearance. Which was commonly done 200 years ago too. You can put the front lock bolt hole high, off center of the nose of the lockplate, but I really don't like when that is done, since it seriously screws up the sideplate side.
With the lock positioned, you can then locate your touch hole. You can move it back and forth a little bit to accommodate your barrel and breechplug. It doesn't have to be dead center of the pan (which can also be opened up some, if necessary). Depending upon whether or not you are using a touch hole liner and the length of your breechplug, you may have to move the breech end of the barrel forward or back some. Don't worry about whether or not the pan fence meets the breech. That's a modern obsession, and while it may look nice, it was rarely achieved back then.
I hope I don't sound like I'm pontificating!
I think maybe I'm making a gun vicariously, since I don't have work facilities ready right now for me to do it myself!
