Holley 670 SA tuning with wideband

This is the combo:
1970 duster
1965 - 273 commando
Cam: Comp Cams Magnum 282S - 282/282 Lift 495/495 (solid) Beehive Springs
Edelbrock D4B intake / Holley 670 Street Avenger
Pertronix Ignitor II & Flame Thrower coil
Hooker Headers
2.5" Dual Exhaust / Super 44 Flowmaster
8 3/4 - 3.55 - SureGrip
727 auto / Shift Kit
10" 2000 stall converter
B&M Quicksilver Shifter

Yesterday a friend helped me to weld a bung for a wideband air fuel ratio gauge (Innovative LM-1). Then we took of my Holley to get a view of the transitions slots, and yes, I was to much into them. So we corrected that and started tuning the idle mixture until we had a satisfactory reading. The transition from idle is now crisp and nice. We took it out with the gauge hooked up, this is the results:
Idle: Perfect
Full throttle: Perfect
Cruising: maybe a little on the rich side
It does however get rich every time I give it gas, so It gets to much fuel from the accelerator pump shot.

Im thinking of going down in size from my 31 nozzle to a 28 (Holley recommends 3 sizes when you make a change), and also going down to 63 on my now 65 primary Jets. Does this sound like a good plan?
Also, it's hard to get over 700 rpm at idle without messing up the idle circuit by going into the transition slots to much. Any suggestions?
Some people (seen after googeling) likes to open up the secondaries a little bit at idle, why is that? Im new to tuning so please bare with me, Im exited about learning and welding that bung on there was a great thing to do :)