Recipe: Homemade Cream Soda from Scratch

Last week I made another batch of soda, but I waited until the batch was nearly gone before posting on it for a few reasons.
The major one being that this is the first batch of homemade soda made from scratch that I've made in a long time, and I wanted to get through the entire process before I began talking about it. This way, I could explore any issues that may have arisen during the process. Thankfully for educational content's sake(and for my own experience), I did have a few things go wrong.
First up, let's talk about the recipe and preparation, then we'll talk about everything that could have been done differently and what may have gone wrong.
I will preface this recipe with the following-this is not entirely my recipe. It is a modified version of cream soda found in Homemade Root Beer, Soda & Pop by Stephen Cresswell. The most important part of this step was that I took a recipe for a 1 gallon batch(10-11 12 oz. bottles), and multiplied ingredients by 2 to make a 2 gallon batch
(which ended up being 20 bottles).
On to the recipe...

2x 6 inch Vanilla beans(blanched)
2x 3 inch Cinnamon Stick(original recipe called for 3 inches of cinnamon bark)
1/2 tsp Cream of Tartar
4 cups of Sugar(original called for 1 3/4 cups of brown sugar-I didn't have that much brown sugar available to me)
Slightly more than 1/4 cup of Raisins(o.r. called for 1/4 cup for a gallon, I used what we had-a little over 1/4cup for 2 gallons)-Coarsely chopped.
1/4 tsp. yeast
2 gallons of water

Bring 1 gallon of water, vanilla beans, and cinnamon to a boil. Stir in sugar, let simmer uncovered for 20 minutes. Remove from heat, stir in cream of tartar until dissolved, allow to sit for 30 minutes.(I ended up letting it sit for about an hour due to middle having a rough time going to sleep). At this time, you'll want to get another gallon of water ran into a pot. After the 30 minutes is up, strain into the other pot(I attempted to strain into my bucket, but I dropped my mesh bag and all of the ingredients ended up in the bucket anyways), stir in the yeast and bottle.
The brew tasted excellent-a bit of sweet vanilla with a touch of cinnamon spice-quite similar to a good horchata. It was magnificent. After 36 hours I checked it-no carb at all.
I checked 24 hours later-and there was a little bit of fizz. Popping the lid off gave a bit of a "psst" sound, and a nice head of fizz came to the top of the bottleneck. A drink revealed a bit of carbonation, but it still needed a little longer. I let the rest sit for another 12 hours and then stuck them all in the refrigerator.
After letting it sit for two days I cracked open a bottle and took a whiff-sweet cinnamon.
Very promising. Then I took a swig-and was very disheartened to taste that all too familiar fiberglass-like flavor I had gotten with my previous, unsuccessful cola batches.
Then I realized-it's got to be the cinnamon reacting with the yeast. Only the batches I've made using cinnamon have developed that awful aftertaste, and it only comes up with the sediment at the bottom of the bottle.
This means I need to two things when working with cinnamon-cut back the amount(which I thought I solved by switching to cinnamon sticks rather then ground cinnamon), and strain it very well.
The brew was more and more drinkable as time went on-and it was always tasty until the sediment had been mixed up. My family still went through all 20 bottles in about six days' time. The flavor was overwhelmingly of cinnamon, though. Next time, I will use the same amount of vanilla, but cut it up with kitchen scissors instead of merely cutting it down the middle and spreading it open, and use half the cinnamon. That way, I can get the flavor of the cinnamon without getting too much in the brew, and hopefully strain out the rest of the stray cinnamon to prevent it from mixing with the yeast too much and getting that unsettling fiberglass taste.
The raisins will definitely stay in the recipe, and I may even add more next time around. I read that they are great for their clarifying properties, and I will admit that for all of my batches of homemade soda, this particular one was the most clear of all of them. It was a nice, clearish off-white akin to many other bottled cream sodas-almost exactly the color of Nesbitt's Honey Lemonade, but with less yellow.
As a bonus, after bottling up the brew I got an amazingly tasty treat-cinnamon vanilla raisins. I might have to make up small batches of those in a sauce pan for the kids and I as a special treat-they were just that good.
So, a few lessons learned. Next challenge to tackle-homemade root beer.