Hi, 200121 is the factory's production serial number, i can only sure AKM 170629 01002 AAD 3620A H is AKM-100SXH 20inch motor.
It seems that the code of the front and the rear motor is different.
The AKM-100SXH rear motor 26inch i have code is :BBC3626A-H, AKM-100SXH front motor 16inch code is...
You can compare with ebay ,AliExpress or other website prices,
Ebay:PSWPOWER https://www.ebay.com/itm/US-stock-48V-13Ah-LG-lithium-ion-Hairon-electrical-ebike-battery-fit-1000W-motor/253725058412?hash=item3b1331256c:g:mG8AAOSwFtZamBNn
Aliexpress: Unit Pack...
You can check it on ebay, there have many choice for throttle
https://www.ebay.com/itm/24V36V48V-Ebike-Thumb-Throttle-with-LCD-Battery-Voltage-Display-and-Power-Switch/263794978898?hash=item3d6b67f052:g:Oa8AAOSw7gZa7BzP
Why not change the KT-lcd3 display, it can set the speed limit and more Features than LED display.
BTW,you can try to check your battery, see if it is your battery's BMS does not limit the output current to cause this situation to happen.
for example:AKM 18040501 001 BBC 3626A
B=reduction ratio
B=motor inner gear type
C=Stator thickness of the motor
36=motor voltage
26=wheel rim 26inch=201,(20=20inch=260; 16=16inch=328)
A=motor type
smartBMS APP can only suitable for Android 4.3 and supports Android device only with bluetooth version 4.0 or higher ,try this Bluetooth Android APP-2.1.1012, see if it can work?