To begin with here's a diagram of the initial state of the cylinder:

For the duration of time when there is still sliding taking place then the friction force is at maximum and therefore the acceleration is a constant and so is the torque on the cylinder. This means the following equations of motion hold:

and

where

and

are the velocity and angular velocity at the point when sliding stops respectively. Also

.

Hence,

can be found in terms of

and

as

.

This equation for the velocity can then be used with the equation of motion relating velocity to distance to find

, i.e.

so then

.

Now all you need to do is find

and

and substitute in the above equation. These two can now be found by resolving forces in the diagram.

Friction force is given by

Resolving perpendicular to the plane we have:

.

Resolving along the plane

.

From these three equations we find that

.

Finally the torque is given by:

where

.

Hence

.

So that gives you

easily enough!

For the second part you can just use the conservation of energy to work out the further distance travelled,

, before stopping. So equating kinetic energy lost to the potential energy gained gives:

then

.