Echostar 8p is/was Octopus Outgoing Lite, which they ditched about 6 months ago iirc, and allowed everyone on Go to switch over to 15p outgoing.
Regardless of what else you do, I would call them and get this sorted out first, and whilst you're at it get them to back calculate to whenever it changed and pay you the difference.
Regarding IOG, assuming you have a compatible EV or charger (a Zappi?), there's no reason not to switch, at which point there's no reason to charge either your EV or battery from solar as it makes more financial sense to do both at the 7p rate and allow any xs solar to be exported at 15p.
I would charge your battery to 100% every night, unless your solar output exceeds your G98/99/inverter export limit.
The benefits of WW are automated battery charging during IOG smart charging slots, smart discharging schedules for xs battery capacity, easy timed quick set charge/discharge (useful for Octopus saving sessions).