A little late at adding to this but the 2.0L Mazda 3 even in MTX is a low to mid 16 second car. ATX I would say closer to the 17 Flat Mark.
Automatics are amazing transmissions it's why my car has remained auto to compete in IHRA Street class Bracket Races. If you would have kept going with this project I would have recommended 22-23" Drag Radials or Slicks, but they have to be small diameter to make up for the gearing disadvantage. N/A nad Nitrous cars love small diameter, short gearing set-ups. Nitrous does alot better on an auto car then manual especially spraying through the gears.
The most important thing no one talked about was installing a high stall torque converter. You will never acheive the times you want with 2.3/2.4 60ft times. Spraying through the shifts I'd recommend an upgraded Valve Body also.
Take into account all the supporting bolt-ons and a 2.3L head shaved down for 10.5:1 or 11:1 compression with a good sized shot on that automatic with the mods listed above and you have a car that will go head to head against a turbo car.
1998 Ford Escort ZX2
Full Bolt-On's, SCT VCT Tuned ECU, 3500rpm Edge Racing Stall, 205/60R13 M&H D.O.T Street Slicks