Use Rhodium's Fucking Search Engine
https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylamine.pdc.html
https://www.thevespiary.org/rhodium/Rhodium/chemistry/eleusis/methylamine27.html
https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylamine.html
Rhodium has a lovely personal site.
And don't forget
googleNow, to address more technical parts of your questions:
1. Yes, the solvent should be protic. Where else can the hydrogens come from? The dissolving metal is the battery, it forces them to move. But they still need to come from somewhere.
2. If they are using BASIC conditions, I imagine the reaction would produce methylamine gas. You could run the reaction really cold to keep it from evaporating, but why not just use an
acidic dissolving-metal reduction instead? Then it would produce MeNH2.HCl, which I can guarantee you won't go turning into a gas so easily.
More to the point, why bother making methylamine from nitromethane at all, when there's much more efficient methods available? Do a hoffmann rearrangement on acetamide and save that aluminum and mercury for the reductive amination! And keep your nitromethane for when some useful aldehydes cross your path!
If you're really so interested in mechanism, I'm sure one of the more knowledgeable staff members would be happy to share their knowledge. All I know is that it's got many steps.