You know what? I would stop using Tots Bots Potion and try the bamboo again with a standard detergent. From everything you've said, it really really sounds like an issue with your nappies, not that the nappies themselves don't work. I tried Potion ages ago... after only a couple of washes using LESS than the recommended dose and still with two extra rinses after the wash, the nappies all had build up and were leaking and/or smelly. So I think that could be your issue. I know you've only used the new ones for a little while but even after a soak they would still not be fully absorbent and then after a couple of washes they could have build up that would make them less absorbent.
So this is what I would try:
Use a standard detergent without softener. Use non-bio if you wish. Strip wash them all with the full dose of detergent method in my signature. I don't think the dishwasher tablet method would be enough. You MUST make sure to do it thoroughly until the water is running completely clear in all parts of the final rinse.
Once they're clear of build up, continue to use normal detergent without softener. Do one cold rinse first, then a long wash (normally 2 hours+) then at least two rinses afterwards. For the wash, only use a tiny bit of detergent for around 14 nappies. If using liquid, look at around 5ml as a starting point; for powder try 10g. Don't skip the extra rinses. Don't be tempted to use sanitiser or anything else. You could look at that later but for now just stick with what we know works, which is the absolute minimum of products.
If you want, before you do this I can compare nappies with you

. If you have some digital scales, weigh a S2 Bamboozle Stretch before you put it on LO. Then put it on him for a set time and weigh it when you take it off. Then I will do the same, we have Stretches too, and we can compare

I know that my LO can easily get 2.5 hours from an unboosted Stretch (using just the one snap in booster supplied) and will stay feeling dry with a fleece liner and it won't leak with a decent PUL wrap over the top. She could last far longer without leaking but might feel damp herself so I wouldn't leave them much longer than 3 hours. She's an average wetter so you can compare your LO.