Just for further clarifications, (I hope this helps all those who are technically inclined):
1) At maximum slip conditions, the torque converter amplifies the torque, but by how much?
Varies from design to design, you need to check specs.
2) Also, this maximum slip condition can typically be sustained for how long before the friction and heat destroy the transmission box?
This is not typical operating condition. You're not even supposed to keep a TC in 'D' if you're stopping for more than a few secs - it should be shifted to 'N'.
, in ICE vehicle we need to race up till the RPM at which highest torque is available and reduce the clutch slip to gently let the wheel start spinning
Sorry, but who taught you to drive like that? Doing this will lead to premature wear of engine, clutch, and tyres. You only need enough torque to overcome the inertia of your car to get moving. You don't need peak performance just to get rolling. Most people don't ever come close to using the engine's peak power/torque.
Even in F1/MotoGP races, they can't use max torque when the light turns green - the limitation is still the grip provided by the (super soft) tyres. The bikes will just flip over, and the cars will do wheel spin and destroy the tyres.
They need to get rolling first with minimal wheel spin and gradually apply more power without causing wheel spin. Heck road going superbikes can automatically do power wheelies when they hit the power band. Hence why traction control is banned (F1)/nerfed (MotoGP) in racing - or driving skill would matter less.
3) In some configuration of motors, there is almost infinite torque (subject to current bearing capacity and heat dissipation capacity) available at 0 RPM
Infinite torque is physically impossible. You can't move a real train using a toy train motor even if you connect it to a nuclear power plant.
A motor will only consume as much current as it was designed for. Typically the max is at stall, where the motor is unable to turn at all. If you continue to power it, it will overheat and get destroyed. EV motors likely have restrictions in place to increase usable life. There's a video of a Reva winning a drag race against a Ford Mustang (BBC G wiz Mustang). But it couldn't have done it without fat, soft tyres.
Otherwise your car's power window motor would crush the glass unless you released the button before it closed completely. The difference between operating current and the higher stall current is how the Auto Up/Down feature works.
