Can I use same product to seal stained table top and chalk paint base?

I have used polyurethane for just about everything and haven't had a problem. You many want to consider spray polyurethane over the chalk base. All finishes will yellow in time.

they make a wax and sealer for chalk paints I would google it to find out the best products to use

I do lots of furniture flips and chalk paint is my favorite paint. I never use polyurethane, it will yellow over time. Use water based polycrylic instead - I like the MinWax brand in the blue can. Wax is what is recommended for chalk paint, but it is more difficult to apply smoothly, in my opinion.