I would also try checking the cores on the client device as the crypto operation may be limited to a single core and limiting throughput. 90Mbit is pretty good.

You've got several session IDs:   (SESSION ID = 5,SA ID = 3) (SESSION ID = 6,SA ID = 2)   we should just look at the second one (ID = 6)   it starts with an IKE_SA_INIT which negotiates sucessfully:   Jul 4 04:02:09.287 UTC: IKEv2:(SESSION ID = 6,SA ...