What is the lifting strength of a 8" I beam that has a 30' span?

Answer 1

There is no such thing as "lifting strength".
What you refer to is the "flambage" (flexion) it will have under a certain strain, and at what strain/stress it will deform or break.
Check in steel manufacturer data sheets: for each profile (I in your case), for each section, you will find the coefficients of Moment for your beam.
From this, you can calculate how much it would "bend" under or supporting a certain weight.
These calculations are of the domain of material resistance, and to calculate the effects, you need to know, not only the moment of the beam, but how it is anchored, where the force is applied etc...