To calculate the new peak lift multiply the 1.6 lift (.480") X the ratio of the new rockers and the existing ones. Your new lift on the intake side is .480X(1.7/1.6).
Not sure what you're asking about. To find out if your valve springs will handle the peak lift without binding you have to measure your existing springs and compare the dimension they bind at to the new peak lift. Nobody else can tell you for sure if you'll be ok - they can just guess at it.
As for piston to valve clearance, no one else can tell what's gonna happen with that either. Once again you have to measure. But the impact with a switch from 1.6's to 1.7's is minimal. The valves are barely open (intake just opening, exhaust about to close) when the piston passes through tdc and the minimum clearance occurs. Because the valves are only open about .08" at that point, the increase in lift due to the rockers is only about 5 thousandths (.005"). But unless you know what you were starting with, you still don't know what your clearance is.
So, if you're gonna install a new cam you need to 1) have the proper valve springs to handle the lift (bind) and with enough force to manage the lobe design - Isky can recommend springs; 2) measure p to v to see if you have enough clearance. You're looking for .080" intake and .100" exhaust. Good luck with it.