What you need are some good trail runners. Here in the states, many ultra-marathon nuts like Montrail's shoes, among them the Leona Divide ($95). It's a running shoe whose mama was a mountain boot, so the Divide has a stiffer-than-normal midsole, beefy outsoles, and a sturdy toebox. All of which should help prevent your toenail woes, while providing stability that likely will stop blisters.
There are other good shoes out there. Asics' Eagle Trail ($90) incorporates that company's gel cushioning, which I always thought was the best cushion system available, and has outstanding motion control. New Balance also makes shoes that are uniformly tough and reliablethe 904 ($105) is a trail-friendly model that you might like. Or, you might even get a light hiking boot, such as Scarpa's Vento Mid ($130), which has the support of a hiking shoe but weighs only slight more than most trail runners. Plus its mid-height cut gives you a little more ankle protection. A real nice shoe.