I believe that the most basic circuit will deliver a current similar to what you want. As an example, see Figure 10 in the data sheet I posted earlier.

With some of the frequencies mentioned; I'm wondering whether that's the root of the problem.

 

With some of the frequencies mentioned; I'm wondering whether that's the root of the problem.

Agreed.

 

I took a look at this post.
https://forum.allaboutcircuits.com/...ncy-smps-buck-converter-using-34063-ic.78805/
The timing capacitor is 1 nanofarad, which resulted in a 26.2 khz output. Will that be good for the transistor?

 

Using a 1 nanofarad capacitor yielded lower current than when I used a 100 picofarad capacitor. 120 ma as opposed to 150.

 

Do you think that the breadboard is creating too much resistance and is increasing the resistance for Rsc?

 

my breadboard was creating too much resistance. I'm transferring the circuit to another one.

 

I took a look at this post.
https://forum.allaboutcircuits.com/...ncy-smps-buck-converter-using-34063-ic.78805/
The timing capacitor is 1 nanofarad, which resulted in a 26.2 khz output. Will that be good for the transistor?

Did you see the size of his inductor? How big is yours and what is the value of its inductance?

Note that at your relatively small currents the solderless breadboard should work just fine if it has not been abused by installing parts with leads that are too big.