How to generate keypair completely offline? Is it possible to generate address and private key pair completely offline, using only dice / other random number generators, calculators, paper and pen? If yes, whats the procedure and formulas used?
Yes, it is possible to create such keypairs offline, but the calculations are long and complex. You would need to find out how to:

1) Create a secp256k1 public key from a private key

2) Perform SHA-256 hashing

3) Perform RIPEMD-160 hashing

4) Be able to convert the final value into Base 58

Generally, the calculations would be very tedious; this is what we have computers for.