Well, first of welcome to WineMakingTalk
Wine is a family of products which evolved out of preservation techniques used a century and two ago. Some of the techniques were still done without much modification as fermenting sauer kraut when my dad was young. AND correctly done they will have barriers which make them as safe as modern factory fermentations.
Many have been studied to say what is happening. Ex. Today we read the add lemon and think "oh this would provide a fence/ pH barrier to keep many families of organisms from growing. Does the mix taste quite acid (have a pH less than 3.7 or better 3.4) -> it is probably OK. If you had yeast growth I would say definitely OK, (yeast make alcohol and 5% alcohol is another fence preventing micro growth). Modern wine is done with sulphite (Campden tablet) (free SO2) which you did not list, sulphite is the last modern trick to encourage yeast.
Unknown yeast is a risk, modern recipies add yeast mainly to make sure they are there doing their job. Sugar is a risk, lots of micro like sugar,,, air exposure without fermentation is a risk -> fermentation produces CO2 which is another barrier.
CONCLUSION; this is something which grandpa would have done and been successful in. The photo has some floating material which I can't identify. If bad it is a slime forming bacteria which does not produce alcohol. (mostly this is a flavor risk) Grandpa had great grandpa holding his hand to say "now taste it, ,,, it should be quite acid,, like lemonade when you start". At this point taste is your best gague, if it tastes off you don't want to drink it when it is finished so toss it. If it still has a clean flavor I would continue. ,,, Going into this with a grandpa recipie (nothing measured) was an experiment in the old ways, in the food lab I will start with some old concept and try to reengineer it (understand/ use modern rules) so that kids with a high school education can do it day after day making a safe product. YUP some things wound up not being the best tasting foods, but the risk of food poisoning with an acidic natural fermentation is low.
