I normally cut back on the feeding to everyother day at around 7 to 8 months depending on their size. I'd also cut back on the supplements to every other week on the D3.
Welcome and congratutations on your first chameleom. Along with the crickets you could offer some small worms such as silkworms. The rule of thumb is no feeders wider than the space between their eyes.
If you have someone to help you it's pretty easty. Hold you chameleon with one hand while you pull down on the chin with the other hand to open the mouth. The second person can now give the meds. ;)