My last job was to design TV mounts, if you go to Bestbuy, Costco, Walmart, Target or any other major retailer I probably had a hand in designing that mount. So to give you some idea of how much studs can hold here is the info from the biggest mount I designed. It was rated for 180lbs, so to UL standards it had to hold 4x that so 720lbs. On top of all that weight the mount extended 28" away from the wall. That would be about 1650lbs acting on the wall to hold the mount to the wall, that mount uses four 3.5" long lag bolts to hold it to the wall.
I agree that doing a through tenon over a half lap will take away so much wood that it will end up being weak.
In my opinion you don't want to overthink it. I would do a half lap joint for the legs, then attach the stretcher with a bed bolt in the center and drill in 1/4" dowels to keep it from twisting. Once you have it built and the stretcher installed with loctite on the bed bolts, you can face glue a false tenon to the outside of the table to cover up the hardware and give it the final look.
I know some people would think that using a bolt is inappropriate, but it is going to create a very strong joint and it will be hidden once you have everything assembled. You can drill the threaded cross dowel portion of the hardware from the bottom of the stretcher and hide it with a plug.
Thanks, this is kinda what i was planning to do after watching some YouTube video's. Perhaps use an oscillating tool at the finish cuts. I'll be using construction glue and a 15ga finish nailer. Want to make sure the new stair noses are on good and proper !
In terms of a straight edge, i may try and use a sacrificial plank of wood (or two) and cut it to the correct width size on the table saw and use that as my guide for the circ saw. Hopefully i don't hit any nails on the circ saw !