Boy, are you brave! I am actually all over the healthy eating, but I have had to accept my limitations in some things.
So that is what I do, do my best to be Almost Vegan. I limit portions in general. I was unable to remove dairy all together, being a milk drinker too. Nothing came close cuz, milk is from animals, not veggies or fruit. I couldn't make that switch. Good for you in your quest to do it though.

I also tried making my own soymilk, being an excellent, sensitive/sensible cook. I was persistent but the results were like yours; the trade off of the Huge amounts of sweeteners, I tried everything, it was not worth it. Water is my best friend. I drink tons.

Wish I had the magic recipe for you. Are you sure you can't drink organic or raw milk? NOT Chocolate, just a good quality milk. I know it's animal so forget that. Sorry.
If not, you may have to resort to your favorite brand of soymilk, but buy less. Sorry. Just wanted to confirm your findings so far.