The testing kit is API Fresh Water Master Test Kit. This kit is extremely important. Water quality needs to be tested to make sure there is no ammonia or nitrite which if present can be deadly.
I would pick up a pair of Reptile tongs also 10 inch and continue to hand feed. Female frogs are better hunters than the males and usually find the food much quicker and over eat.
Frogs tend to lunge at their food and can easily get hurt with tweezers if they are sharp or pointy.

What size tank are they in? Are they still in the tiny cube thing 4 inch by 4 inch? If so they need a larger tank ASAP. The advice you got in the thread you linked to is great advice - I would reread.
If you cannot afford to pick up a larger 6-10 gallon tank right now, then look for at the minimum 3 gallon for the time being (can be used as hospital/quarantine tank later) and do a few water changes per week with Prime. In the meantime you could fishless cycle another tank when you get it. Sooner rather than later would be best. They also need their water temperature at least 78 degrees so you need a tank that can accommodate a heater and thermometer.

If your Betta is tormenting the frogs, the frogs can be stressed out and stressed out frogs/fish can lead to health problems. Bettas have teeth so they can easily injure the frogs. Frogs have very poor eyesight and no teeth and a quite defenseless, but do to their poor eyesight they can easily mistake the Bettas Fins for food. Some folks have no problems housing bettas with frogs but lots have. I personally would not house them together especially in a small tank. ADF's are always do best in an ADF species only tank.