I did a search for a few vegan soy milk mayo recipes and the first three I found did not include the regular mayo rest period.
When making mayo with eggs, the acidic, fresh, mayo is allowed to sit at room temperature for a few hours to kill off some potential bacteria before refrigeration shuts everything down.
First of all, the recommended period for this rest is around 8 hours not two days. Secondly, your risk of harmful bacteria is much lower as you are using processed ingredients instead of raw eggs. I would leave out the rest period altogether.
As for your results- As Stephie wrote, the bottle that was fizzing needs to be promptly discarded. Evidence of active bacterial action, unless you are intentionally fermenting, is a very very bad sign. Don't mess with it.
As for the other. Soy milk is fairly fragile; acidity and more so calcium can cause it to curdle into tofu. I wouldn't expect the acidity of the mayo itself to curdle the milk because there isn't that much milk and it is emulsified and thickened with gum. However, your curdled mayo is actually another sign of spoilage and you should throw it out.
In the future, to prevent this happening again, I would recommend simply not giving your mayo a chance to spoil and refrigerating it immediately. You might also experiment with using silken tofu instead of soy milk which, I've read, produces better results.