Just doing some maths OP which I’m sure you’ve already looked at but...
OP salary £60,000 = take home £45,400/yr ( exc pension payments )
DCdad salary £100,000 = take home £68,560/ yr ( exc pension payments )
If you both pay an equal share of the fees
OP £45,400 - £15,000 = £30,400 to live on and pay pension, Uni fees etc
DCdad £68,460 - £15,000 = £53,460 to live on and pay etc etc
Im not reducing this figure by the child maintenance as OP has costs for that too.
Can you live on £30,400 OP ?
Can DCdad live on £53,460 ?
According to websites for calculating uptick in fees in 7 years your fees could be approx £38,000……will salaries keep track to pay this or perhaps you can use savings if not. If salary increases are based on % of salary you ex will in real terms get a bigger rise than you each year, so it’s worth remembering that.
IF you pay a share of the fees on a 60/100 ratio based on your current salaries
OP £45,400 - £11,250 = £34,150 to live on
DCdad £68,460 - £18,750 = £49,710 to live on
Perhaps these figures will help you make the decision OP.
( brain training for me for day done )