You can find that wrench tool at any large gun show, where somebody has a layout of M1 Carbine spare parts. Very easy to find. Asking price runs between $10.00 and $15.00 in my experience.
As for using lead ammo, I have seen that most carbines start to jam after just 150 or so of the regular fmj rounds, not from the lead but from the gummy GI type powder. So, if you are adding lead bullets to the mix, then yea, you are definitely going to run into jamming problems after just a box or two of ammo.
And (here's why I don't like the Carbine), that gas port is not just a "snap" to clean. Breaking down the gun to get to it, unscrewing that nut, and cleaning that port is a total pain in the butt! And it takes time. (You have to really clean the barrel well at the same time.)
Be sure to buy a good supply of pipe cleaners for use in cleaning the port. You will need them!
Regards,
Mannyrock