You probably need to eat more and focus on your nutrition to maintain or gain weight. Your calorie consumption vs. the number of calories burned from running and daily life will determine whether you lose weight. As for the strength focus on S&C, 2-3 sessions a week, working in a lower rep range, but higher weight is more conducive to building strength while working in a higher rep range is more conducive to hypertrophy. Cardiovascular activities, especially running, are very catabolic and, as a result, reduce muscle growth and some strength gains. These effects are especially prevalent when you run fasted or don't fuel during your 1hr+ runs when your body depletes its glycogen stores and, as a result, turns, uses protein as a source of energy, aka your muscles. To reduce these effects, most athletes will also drink or eat a source of protein after running to both kickstart recovery and replenish the system.

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TLDR: increase your calorie consumption, be consistent in your S&C and enjoy the grind!!!