To get the max of your current setup all you need is a new fuel pump, boost controller and a tune (Nistune or a full standalone ecu)
Seeing as the engine is a bit built just tell the tuner you choose to take it to where he thinks is safe
No idea what those turbos will go to but probably near 300kw, probably be limited by the injectors so yeah whatever is safe on those
If you want to run e85 in the future you should go for a high spec ecu so you can run an ethanol content sensor