Don't rely too much on the surface intervals. Freediving DCS is stil purely studied and understood, and the number of cases studied, unlike at scuba, is quite limited. Unfortunately most of advices are based on algortihms and methodics developed for scuba, but there are more factors involved with freediving (especially high CO2 levels, hypoxia, stronger pressure gradients, bradycardia and vasoconstriction, different metabolism and thermoregulation, fast ascents, physical effort, etc, etc.). Look up DCS here on the forum, especially the posts of Eric Fattah. He has been bent several times, and has a lot of experiences to share. His Xen computer is also the only one on the market with an algorithm helping to prevent DCS at freedivers. Eric's opinion is that the surface intervals won't help much. Be sure to check out his comments on this topic. Doing repeted dives to 20-30m during two hours, despite 6 min surface times does not exclude bents. There are couple of things you can change to reduce the risk - for example proper hydratation, slow ascents, short apnea deco-stops, or at least recompression decos, or even deco with compressed air or O2, etc.
If you have the slightest suspiction of past decompression accidents, I would strongly advise visiting a specialist. An MRI and CT scans could reveal neuronal or sceletal necrosis. They may not help with the diagnosis of a light DCS after such a long time, but could detect some damage after repeated cases. I believe that the easiest diagnostics is actually recompression - if the symptoms disapear after recompression, it is a clear sign of bents. So if you ever experience some DCS symptoms in future (incl. unusual fatigue, pain in articulation, especially in shoulders, marmor skin, itching, formication,...) you better contact immediately a diving doctor, and get a check very fast without waiting the next day to see whether it gets better.