If you do a search you should find a detailed repair procedure for the seats:~
Not sure if it was this forum that I took the details from but you should find it.
The foam is not that unusual regarding splitting but can repaired and the seats reinforced with a heavy weight cloth such as calico- this is glued into place and does make a real difference.
The procedure isn't that difficult just a bit long winded (I used heat resistant spray glue) and rather than the hog rings used small cable ties.
Additional webbing is also a worthwhile task.
The covers also respond to being washed in warm water & detergent- not a hot wash-do them by hand.
One link is here:~
https://www.volvoforums.org.uk/showt...ht=front+seats
https://forums.tbforums.com/showthread.php?t=195389
Hope it helps.
Bob.