There are some interesting pictures at this site

http://www.ornithopter.org/flapfligh.../birdsfly.html

There are a host of sites that discuss bird flight including some that put trained birds into wind tunnels to study their flight.

On the forward sweep thing. It is a compromise. The wings need to fold completely into the body to protect the flight feathers when hopping about the ground and to retain some body heat. There is the necessity of folding the wing on the upstroke to reduce the drag during that portion of flight. With those requirements and given the limitations of an organic bone joint/ligament system a compromise of that angle verses aero effectiveness of the wing produces what we see. Each reduction of angle between the bones allowing the wing to be straighter makes the complete folding of the wing that much harder. Forward sweep angle effecting stall is not a factor with the dynamic flight system that the birds possess.

The tip feathers depends on the type of flight. Two extremes are the albatross and the buzzard. Dynamic soaring flight based on the wave motion of the ocean (which is fairly constant) which is what the albatross uses seems to be most effective with a very aerodynamically clean high aspect ratio flight. The buzzard doing thermalling flight in which the magnitude of the thermals may vary from a little to a lot uses the separate wing tip feather system. Each feather acts as a slot for the feather following it. With some control over the slot action the lift characteristics of the wing can be adjusted.

In both cases the twist of the tail seems to be a primary directional control surface.