One additional question. If I am using a spider box fed with 50 amp 240V. Does this provide me with 100 Amp of 120V power since its two 120V feeds of opposite phase?
Sort of. If you are pulling four conductors, Leg A, Leg B, Ground, and Neutral, with Leg A and Leg B 180 degrees apart and at 120v each, then you'd get a 50A chunk of 120v on Leg A and another 50A chunk of 120v on Leg B. This is not to be confused with a 100A feed, because if either pole of the 50A/2-pole breaker sees over 50A, it'll trip.
Should all of those "if" conditionals be met and your distribution box be [appropriately configured], then you'd see the following results:
Leg A - Leg B - Result
40A - 40A - No Trip
60A - 0A - Trip
0A - 60A - Trip
50A - 50A - Eventual Trip
So theoretically, you can have access to 100A @ 120v, but not in a single chunk and practically you'd only be able to use ~80A continuously and ~100A as an instantaneous max to prevent tripping the breaker.