750 is too lean IMO for gas, considering the narrow band sensor is not accurate, error on the rich side so closer to 800.
Raising the pressure is just going to put more strain on your pump, you need injectors that are at least 30% bigger and that will only sustain your current power level. So if you bought 60lbs and are around 80% duty cycle then getting an injector only 30% bigger for E85 will still leave you at 80% duty cycle with barely any room to grow HP wise.
Dig around here, there is tons of talk about what mods you should consider doing and my opinion on fuel pressure with the stock Walbro.
I wouldn't put the stuff in your tank until you really have a handle on what E85 is and does.
Eric at Turbotweak has chips for E85 and is a good guy to bounce ideas off of.