You should not need antifoul in fresh water, but suggest you ask other boat owners on the lake/river what they use if any.
No there is no external drain for the bilge. There should be no water in the bilge anyway. If there is then you need to find the source of the leak and fix it. Leaks are usually from the fresh water system - the only such leak I had on my 37 same as yours was from a split hose on the calorifier, but other common sources include the shower on the transom. Seawater leaks are usually from either the engine water pump or the muffler when the ends corrode. Other leaks from outside are usually through deck fittings or stanchion bases. Water that does get into the bilges can take time to drain down to the pump sump because the cross ribs that reinforce the hull are hollow and water gets trapped in them, but drains out over time as the boat moves.
Once I solved my leaks my boat was dry for the rest of the time I had it.
