Hi, i find pretty odd that high point players get no points win/loss in a game where average player have lower point than him. I think they should risk more for less that way you would need to maintain a good % win/loss to be able to maintain a high PSR. In this manner i would propose a formula that look somewhat like this :

Calculate both teams PSR average :

Example :
Team 1 Total : 7000 - Avg : 1400
Player 1 : 1200
Player 2 : 1300
Player 3 : 1400
Player 4 : 1500
Player 5 : 1600

Team 2 Total : 8150 Avg : 1630
Player 1 : 1500
Player 2 : 1550
Player 3 : 1600
Player 4 : 1700
Player 5 : 1800

Now lets says for each game the base bet is 25 Points :
Since team 2 average is higher they have better chance at winning, so if they win they should indeed win less poins than if team 1 win.

I suggest direclty using the team total ratio
Exemple :
7000/8150 = 0.8588
now take the base win point with the team for lowest average is :
25 / 0.8588 = 29.1
if they lose :
25*0.8588 = - 21.5

for the team with highest average its the inverse
win = 25*0.8588 = + 21.5
loss = 25/0.8588 = - 29.1

Now u also need to account for individual player skill :
in my opinion a high PSR player joining a game with low PSR should win much less point then he risk losing since he is playing against people with less skill - i would consider this manner as the follow

for each difference the player have regarding the other team avg PSR he will get a malus (or a bonus if he has a lower PSR) to his win/loss point.

Example :
Team 1 - Player 1 has 1200 points
Team 2 average is 1630
(1200 - 1630) = -430

Let stay for each 100 points difference u get 2.5 pts bonus / malus per 100 pts difference

-430 * 2.5 / 100 = -11

Win points are affected as follow : 29.1 - - 11 = +40.1
Loss points : -21.5 - - 22/2 = -10.5

Also i suggest implementing Loss/Win streak
for each consecutive win ud get a bonus +1 points to ur PSR
and for consecutive loss -1 PSR
mean if u have a 10 win streak u get + 10 PSR