At the rate you have it for self healing a normal welder would be able to only heal almost twice on average before needing more fuel. So its only worth 60 HP at best, if I am understanding how augs work.
30 fuel in normal welder, 5% chance of loss of 1 fuel per tick [wow I did not know it was like that, especially with byond RNG being what it is], 150 ticks on "average" before it runs out.Thus two uses of 80 ticks (you might not ever get the second use).
Currently its 80 for self healing, and 20 for healing other, for healing other it would be on average be 7 uses before it runs out of fuel, which is okay I guess.