could there be lead in the wood sealant on my 1930s table?
It's possible. Lead acetate was a common drying agent used both to accelerate the cure times of clear varnishes and to chemically produce boiled linseed oil. Given the table vintage there's a high chance that any clear film finish is actually lacquer, which can be removed easily with lacquer thinner. I'd test a small section and see. (Shellac is another popular sealant, but it seems unlikely it would contain lead. In any case, shellac dissolves readily in alcohol.) With any luck you can simply wash if off with the appropriate solvent once the paint is gone.

If all of the paint doesn't scrape off easily your best bet is going with a chemical stripper and taking it all down to the wood. A couple of brands use sheets of paper that keep everything together, which is ideal for dealing with lead. You should definitely avoid heat guns, because lead compounds tend to vaporize at low temperatures. (Hence the use as a drying agent.)