As long as your EMT is properly bonded at the line end your plan is fine "where installed on buildings" 680.21(A)(2).
Your first question gets into the difference between the grounding and bonding conductors George was talking about. The 8ga is the equipotential 680.26 BONDING grid and that is not required to be connected to the ground bus in the panel. 680.26(A)FPN
The objective is simply to bond all of the metal that touches the water, and out from the deck 3' (2005) in a solidly connected grid. Those 8 ga wires can have "Connection shall be made by exothermic welding or by pressure connectors or clamps that are labeled as being suitable for the purpose and are of stainless steel, brass, copper, or copper alloy." 680.26(C)
The conductor that must be made without joint or splice, is from the panel to the listed underwarer water "J" box (aka deck box, although they will be out in the yard, as often as not. The excewption to the "without joint or splice" is a busbar in the timer or listed switch enclosure. 680.23(F)(2)ex.
This is going to be a 12ga or larger insulated wire.
The pump also requires a 12ga or larger insulated equipment grounding conductor but the code is silent about splices. Some inspectors still like to see it unspliced. YMMV.
The whole issue about whether this is grounding or bonding and in fact whether the pool becomes a grounding electrode will usually start a fight in an inspector meeting. The fact still remains that the 680.23 "bonding" grid is electrically connected to the required "grounding" conductors at the pump, the light, the heater and the underwater speakers so the electrons will go where the EMF drives them.
I decided in my pool to just bond the spa grid, pool grid and panel GEC bus to a common copper bus with a #8 and stop making the distinction. I am grounded/bonded six ways from sunday. I am hoping, when the lightning hits, all of that juice finds it's way to ground as fast as possible.
