Yes, one more land target - it adds some flexiblity for the RAF and uncertainty for the LW. NO the LW should not have more than 50 mi of radar range.
It is so tough to answer the other questions- so much depends on the situation. But as a starting point, I'll guess that in an engagement against an escorted Lancaster bomber force, 1/2 the intercepting force will be engaged and tied up by the escorts, while the other half gets through. And each of those late-War LW fighters that gets through will down an average of 2 Lancs, one before the bomb drop and one after.
So with an attacking force of 48 Lancasters and 32 defending fighters - 16 intercepting fighters get through and down 32 of the 48 Lancs, but 24 Lancs are able to drop on target.
If you want 50% of the bomber force to survive, I recommend increasing the size of the Lancaster force to 22 from 16, or reducing the size of the LW fighter force from 32 to 24, or some combination of the two.
Just a starting estimate for discussion. I am not sure how reasonable my assumptions are but you have to start somewhere.