With small planes I like to give them a couple of test glides to test the controllability, balance and throws. I look for a soft level or slightly sloping landing zone about 100 feet long oriented with the wind. Long grass or soft snow is ideal. I run a few steps and give the plane a firm push straight ahead into the wind and then fly it till it lands. Don't throw it up or down, just push it straight ahead firmly. If it tracks straight ahead without stalling or diving and with little or no transmitter input required, I consider it ready for a power on test flight. If I have to get on the sticks immediately to prevent a crash then something is wrong. I make adjustments and test again. Power on test flights are made with about 2 or 3 minutes of fuel onboard.

On another point 30 degrees of throw is probably WAY too much on any flight control surface except maybe the rudder. I have planes that are very sporty with 10 degrees of throw or less. If your plane is properly built and balanced you shouldn't need more that 15 degrees to 20 degrees of throw.

The picture that you have posted makes the propeller look much larger than 5 inches, it looks like 9 inches or so. A 5 x 3 prop is great for a faster plane but I find slower draggy planes fly better on a 6 x 3 or even a 6 x 2. APC makes a 5.7 x 3 which is very nice for high drag planes I think it would be ideal for your biplane. I have a 2 meter glider that climbs with authority using a Cox Medallion and an APC 6 x 2.