I would like to increase water pressure on lines in my house. Now if you flush a toilet and turn on a faucet?

First of all, check your well to see if you are pumping enough water. Who determined the well is shallow? If you can get the water pressure up to where you want it will this cause your well to go dry? Is the water pump doing its job? If the answer to those questions are all ok then its time to check the water pressure at the house by testing the pressure at the first available fitting. Determine the pressure there. If it is too low the problem is between the house and pump (cracked water line)? If all is ok there (45-55 psi), I believe as city water pressure where I live is near 55 psi. So, all is normal and you want to increase the water pressure? Do a visual check for a pressure valve. For the last 30 years or so a standard pressure valve was used in most homes. The valve appears bell shaped and is brass. If this is the one you found there is a lock-nut on one end. Loosen that lock-nut and adjust the screw clockwise (in) 1/2 turn and then check your water pressure in the bathroom. You now know how to adjust the valve so if needed go another 1/2 turn. You may have a different looking pressure valve but I'm sure you can tell the difference between a shut-off valve, a ball-valve? If a pressure valve wasn't installed (which I wouldn't consider since you have a well), then you'll have to have one installed. Copper piping is strong and you need not to worry about this. Looks like you may need a reputable plumber.

I have municipal water. Water pressure is 80 psi. No leaks.

You need both pressure and volume. You should have at least 40 psi, 60 is better. Your pump may be on its last legs or you may have a leak between the pump and the accumulator or a faulty pressure regulator if you have low pressure. Good pressure but low volume (due to a restriction or clogged filter) would cause your issues. You can buy a pressure gauge that attaches to a hose bib on the outside of your home. About $15 at most hardware stores. See what that pressure reads. Your system should be able to provide enough volume and pressure with just a toilet and faucet running.

Summary:

Low pressure - pump problems or leak between the pump to the accumulator or faulty pressure regulator

Good pressure - clogged water line or filter