Yes, I think you may be overthinking a tiny bit about the foxgloves, but I know that we all want the best for the hogs, so it’s easy to overthink from time to time. But, I imagine foxgloves must have been growing in the wild for a long time, so hogs would have become aware of them historically and know whether they needed to avoid them or not. I sometimes have foxgloves which appear in my garden and they don’t seem to have had any impact on the visits from the hogs. I imagine they just ignore them.
I’m not sure about the seaweed, but if it was too salty maybe some plants wouldn’t like it? But I believe there are other salts in seaweed than sodium salt which might make it less of a problem and more beneficial to some plants? I’m guessing that you wouldn’t be using it on lawn area, so maybe the hogs could still catch worms there. It might be a question of how much you use and how much of the garden is covered in it. But bearing in mind how much good worms do for soil structure, I don’t imagine anyone would want to do anything which reduced numbers of them too much and seaweed does seem to have become more popular for mulching, etc. Once any salt has been washed out by the rain, the earthworms might like it. Maybe more research needed. It would be interesting to know any observations that you make when using the seaweed.
But if you are supplementary feeding the hogs I expect that they would continue to visit your garden for that.