I know this sounds complicated, but hear me out.
Start everyone out at 500.
If at same ranking, winner gets +1, loser gets -1
If winner higher ranking, gets +1 +1/8 of diff rounded normally up or down to whole number, loser gets -1-1/8 difference rounded to nearest whole number
If winner lower ranking, winner gets +1+1/4 difference rounded to nearest whole number, loser gets -1-1/8 of difference rounded to enarest whole number.
If a king of the hill match, winner gets +5 in addition.
For example rating 501 beats rating 507. Winner gets +1+(6/4=1.5, round 2)=1+2=3
Winner new rating 504
Loser gets -1-(6/8=.75 round 1)=-1-1=-2 Loser new rating 505
If a 507 battles a 495 in a gking of the hill and the 507 wins, the 507 gets +1+(12/8=1.5 rd =2)+5=1+2+5=8 New rating 515. Loser gets -1-(12/8 rd =2)=-1-2=-3 new rating 492.