For highest accuracy it is recommended that the ICL7107 ampere meter module should be supplied with its own voltage supply. If measurement of the current of the same supply is needed, ICL7107 ampere meter would have to sample negative not positive voltage supply.
Brightness of the LED displays can be varied by adding or removing 1N4148 small signal diodes that are connected in series. Use two 1N4148 diodes for higher brightness.
Also, the use of 7805 5V voltage regulator is highly recommended to prevent the damage of ICL7107 and 7660 ICs. .