Issue is you are fighting physics now. You've already tried Exitlag and that will be your best bet going forward. Unless you can move down to CPT get a touch lower ping, this is it.
I'm on CISP/MFN 1gb ,
Overwatch latency (I'm also using dropship to force only playing on Amsterdam, Blizzard...
Been playing Dia+ matches, servers are ass. Been testing with Exitlag (Mostly been using it.) and without it , spiking to 170-240 at random until < 7 teams
Even my EU mates are suffering from the same issues jitter + choke. Servers have been a joke this season.
Its in London // Hyperoptic Limited London speedtest server , the ping pretty much confirms it 160~ and no VPN. Just note it is multithreaded , on single thread I get 220-240~DL/270~UL - So happy days really.