using elliptic curve point multiplication as a key stretching method
If I understand correctly is to hash your password $pw$ into a point using either $P=Pad(pw)\cdot P_0$ or $P=MD5(pw)\cdot P_0$ and then use $P$ for cryptographic purpose. The exact security of this proposal depends on what you want to do with $P$ exactly. But in some case, this is not secure. Typically, this mechanism is not a good way to hash a password (even if you add salt by varying $P_0$).

Indeed, in this application, you would know $P$ and $P_0$ and recovering the password $pw$ could be done using a discrete logarithm computation. Since $pw$ is generally quite short, $Pad(pw)$ belongs to a short interval of length $N$ (where $N$ is the number of possible padded passwords). In this case, using Pollard's lambda (i.e. The kangaroo method) allows to compute the discrete logarithm at a cost of $\sqrt{N}$. With $MD5$, $N$ is $2^{128}$ which would give a cost of $2^{64}$ to compute the logarithm, probably not enough.

On the other hand, if your application keeps $P$ secret, this is probably not going to apply. So could you tell more about the exact use of $P$ ?