Phantom711

Just assign that button to „Weapon Select Switch Right“. There is no need to use a modifier.

The Engine-ANTI ICE…yes definitely. If you fly through clouds in cold weather the engine icing warning will actually come on if you don‘t. It will also extinguish after some time, when you turn ENG ANTI ICE on.
The others I don‘t know, but I would guess it‘s not modelled.

You‘re overthinking the racetrack pattern there too much. This is not an IFR holding. You can just eyeball it on the SA page. If you were given A5, just be roughly in the north and NOT CLOSER than 5NM to E.
In terms of system usage, I wouldn‘t even bother to make A5 a dedicated point. I would just put in E and then use the CRS line accordingly in order to stay north.
P.S.: Since it sounds like you are quite dedicated, check out my sig! We are looking for new Hornet pilots.

The paddle deactivates NWS.
To activate NWS you need to press the NWS button. 
Are you sure, you didn‘t accidentially mix that up?

Well…then don‘t select A/A guns if there is multiple aircraft in front of you!
Select AIM9 or AIM120 first. It doesn‘t even matter, if you have any on your jet. Now you can use boresight or whatever ACM mode you like with or without the HMD. After you have acquired the lock you can now select the gun.

Unlike @speed-of-heat I would say the F/A-18 throttle grips are a solid choice even for other modules unless you are eyeing the A-10 or F-15 modules as well. There is simply no second guessing on which button to bind for the Hornet.
As for the throttle base: it is not meant to be a Hornet replica but is still a little Hornet inspired. You might still want to choose to map buttons differently from what the base labels say. 
If you can squeeze out a bit more money, also take a look at Winwings Take-off panel (PTO2). It gives you a nicer gear lever and it frees up some more buttons/switches on the throttle base. The layout is also relatively realistic for the left front quarter panel.
I‘ve never owned a Winwing stick, so I can‘t say much about them. 
Thrustmaster (TM) also has a Hornet stick, but the buttons on that are a bit lower quality. It‘s not too bad though.
TM also just releases a new stick base, the AVA base, which seems to be quite good. Other than that, a TM stick can also be put on Virpil bases.

NWS works as advertised for me. Can‘t think of anything, you are doing wrong.
As for the DDI buttons:
 

@CoaCoaPuff
Hi…
I have the WW F/A-18 throttle, so I can only guess for your problem, but I try:
 
1. in SimAppPro make sure the ANT ELEV knob is configured as an axis.
2. In the DCS controls config menu: choose „Axis Commands“ and then select ANT ELEV. (I am saying this, because you could also assign ANT ELEV up and down to buttons and then it wouldn‘t recognize if you move an axis instead).
3. When you assign the axis, move it all the way to the extremes. I‘ve observed, that it is only then being recognized and assigned.
 
Hope this helps.