The thing you have to realize about Hawking radiation is that for mosr black holes, it's not very powerful. The power scales inversely with the square of the mass of the black hole:
$$P=\frac{\hbar c^6}{15360\pi GM^2}$$
The upshot of this is that a black hole of $\sim10^{6}\;\text{kg}$ would be only one-millionth as luminous as the Sun, or, according to Wolfram Alpha, comparable in power to a hurricane. This black hole would live for 1.4 minutes; if you chose a black hole that would be stable on geologic timescales - say, one million years - then the emission would be even less intense.
As a rule of thumb, if your black hole is stable over human timescales, it won't produce dangerous amounts of Hawking radiation, and a black hole is only dangerous in the very last moments of its life. You'd have to reach exceedingly small masses for it to be problematic at all. The lower limit, then, is bounded not by Hawking radiation but by how long the black hole has to live. For instance, if we want a black hole to live for 1000 years, then its mass will be $\sim7\times10^8\;\text{kg}$, and it would produce about $2\times10^{-12}L_{\odot}$. In outer space, it would be virtually undetectable, either from its radiation or its gravitational effects.
Now, the tidal forces from a black hole of mass $M$ at a distance $R$ are no different than the tidal forces from any other body of mass $M$ at a distance $R$. We only say that black holes have strong tidal forces because they are so compact, and therefore you can get quite close while remaining outside them. In other words, the tidal forces 10 km away from the center of a black hole are no stronger than the tidal forces 10 km away from any other object of the same mass smaller than 10 km.
From the above, we can imagine that a black hole on the surface of Earth that survives for about 1000 years can fall into the mass range of $\sim10^9\;\text{kg}$ (below which it will evaporate) and $\sim10^{14}\;\text{kg}$ (above which the black hole begins to have a gravitational pull significant in comparison to Earth's within a few hundred meters of it. Outside a few kilometers, the tidal forces are no stronger than that of the Moon. For that black hole of $10^9$ kg, we could go within 1000 feet before the tidal forces became that strong.
A black hole within the Solar System can have a mass comparable to that of, say, a massive moon before it begins to have a gravitational or tidal impact, depending on where it is. If it's no closer than the Oort cloud, it could be of planetary mass and still pose no threat in terms of gravitational disruption; if it's closer than that, perhaps being comparable to a high-mass moon could lead to problems.
