Sounds like you are not treating it as a bog per se but rather an acidic substrate for appropriate plants. If just regular vascular plants and not any specialized bog plants will be planted then sure you might check out a product such as Miracid acid plant food and use as directed. But if you are planning on growing specialized bog plants, such as any of the pitcher plants or sundews, then you need to forgo using any type of soil amendment other than more sphagnum peat moss.

I think that's accurate. I call it a bog only because it has deliberately poor drainage. Should I wait to see if plants need more foil or nutrients or just assume they will?

The number of plants in the planting will consume nutrients as needed. Fertilization should not be like feeding a herd of cattle where food is dumped in a pile and the animals feed, rather a continual low dosage feeding over a prolonged period when the plants are in active growth and development, such as in flowering. This way the plants will get enough and the soil mix will not become over saturated with fertilizers that could create a new world of disorder for the plants' root systems.

Probably best to flood the area to help dilute salt build up. Frequency of flooding is naturally on a daily basis in spring and winter and less so in summer for bog type settings.