Yes the colon is a standard habitat for candida. Candida joins in long chains and drills into the intestinal walls in oder to reach for the bloodtream.
Your plan is a good start. The regimen + magnesium, vitamin B, potassium and omega 3 supplement. Then a colon cleanse.
Candida strives due to an overloaded liver so it is then a good thing to do a liver cleanse and often also a kidneys cleanse. THe idea is to cleanse your cleansing organs so they can perform better.
Oxy Powder is a good cleanse, but because candida is stuck to the intestinal walls, it wont be enough to get rid of it. Enema (colema of colonics) must be used along and in my opinion, psyllium husk or the P & B shakes is the best way to clear candida out.
Oregano Oil, Pau d'arco, and Garlic are all antifungals. Avoid using the full dose of each if you use them to gether - rotating them is the best as you might know that using only one of them will let candida develop immunity towards the specific antifungal you are using on a permanent basis.
Later on when you want to introduce probiotics you might want to stick to oregano oil and grapefruit seed extract since they kill the fungus but not the friendly bacteria.
Magnesium supplements is a good way to help prevent constipation. Mag. deficiency causes constipation (and enemas can be helpful too especially when you start expelling candida).
I also have candida in my sinuses and I find the NeilMed Sinus cleanse to be fantastic (this brand or any other brand which uses BOTH salt and soda- the salt cleanses and the soda prevents candida from growing back). You can find this cleanse at your local drugstore or order it online.
When I did the liver cleanse (long before I found out about the sinus cleanse) I finally was able to gain back the sense of smell. So that is another thing you should try.