The robot arm is approximately 8 kgs and is lifting a weight of 12 grams (reach=1 m).
Another solution would be to design the arm to be much lighter. 12 grams does not require an 8kg arm to hold it one metre away. For example, a 30mm carbon fibre tube one metre long weighs 200g, adding a couple of pivots and rods for actuation should still be under half a ...
If I understand correctly, your motors do not have enough torque for the given mass distribution in the robot.
There are a few suggestions to handle the issue
Use two motors at joints closed to the base that observe the maximum torque. (I would suggest doing some calculations about maximum torque requirements doubling up the motors). However, there would ...
Use gears, adding second one will increase the torque, but it's better to have 1 motor instead of 2. You can also add a gt2 pulley that increases torque decreasing speed. Replacing this motor with a stronger one will also help. If your motor's max speed is too high, I recommend gears or a pulley, so speed won't be too high.
The IRB140 has no horizontal shoulder offset as the classical Puma 560 has. This means that there are not different "lefty" and "righty" solutions. There is still a possibility of elbow up/down and wrist flip/noflip solutions. So I think there are, in general, only 4 solutions for this robot.