I am by no means an expert on this topic but wanted to chime in. I wonder why the ph is so high? Is is Calcium carbonate or salts of some kind? Here where I am the Calcium carbonate levels are very high in the water and often in the soil. Adding sulfur will change a percentage of that to gypsum but isn’t going to move the ph that much. Organic matter does seem to work to lower the ph some.

My hypothesis is that increasing soil biology will be a better route to take than ph changes. Your focus would be on driving nutrient exchange in the root zone where the plants are needing it. Sulphur is going to have a negative impact on soil biology so it might no be helping to grow your crops.