If a go-around is required, the PF will therefore need to manually establish go-around attitude and set go-around thrust.
So, my questions are:
1. Should the PF manually establish full go-around thrust (as depicted on N1) or set a reduced go-around thrust, and if so, what is the target N1 for the reduced go-around thrust?
There will be differing opinions. I know there are some who insist on full power then reduce, once established with gear up, if applicable. There are others who suggest to do the same as the automatics i.e. single TOGA. This gives 1000-2000fpm and satisfies relevant performance requirements. How much? I find 85-90% is more than satisfactory. If will be aware of your LDW and so can choose a number in that range. It needs briefing as PF needs to advance the TL's manually and then call "set thrust". I've seen it so often in the sim where PF sets a good reduced N1% and then PM shoves it up to full. Causes a little surprise and a WTF moment. This assumes both engines thrusting.
2. Boeing QRH Man. chapter states that the autopilot can be engaged as needed for a manual go-around, but does not say anything about the autothrottle system. As I understand it, the A/T should be manually re-engaged on the MCP during the go-around. At which point should that be done?
Same time as AP. There is a difference of opinion which comes first. Boeing changed the sequence order a few years ago. Check your SOP's & FCTM.
3. After pressing TO/GA, the AFDS will engage in the go-around mode. If an A/P is engaged at that time, will the pitch mode stay in GA? And, shouldn't the A/T be armed at that time as well to comply with Boeing recommendation to either be fully automatic or fully manual.
FMA's will change to the same as pressing LVL CHG. Some operators have SOP's to fly manually until Flaps UP. There is an idea that coming out of GA and into MCP SPD is detrimental to the GA profile. Not sure why they think that as you would most likely delay AP engagement until you are relaxed, in trim and probably 1000' & climbing. For A/T engagements see #2.