Converting Road to MTB shoes...

I assume that you were able to fix the cleat.
That means that your soles have a "Lancia grill" style double slot, correct ?

You have to glue some kind of tread on the soles.
As a matter of fact, Shimano used to sell these to shoe factories to be 100% compatible. But these were never available to end-consumers.

The thickness of the tread is critical.

Too thin: shoes / feet instable on the pedals (wobbling)
Too thick: hard or even impossible to (dis)engage

In the early days of "clipless MTB racing", several racers used to take road shoes (carbon soles) and glued MTB outer soles on them. This mad a very stiff MTB racing shoe. Most SPD/ATAC compatible MTB shoes were too soft/flexy for racing.
Nowadays, there is a good choice of stiff offroad shoes.

Yeah can fix the cleat, I'll look into glueing something to the bottom and see how I get on. cheers