You don't have to worry about valve damage - the only B230 that's an interference design is the 16-valve, twin cam version. One less thing to worry about.

It seems to me your engine is mis-timed with respect to valve timing, even in spite of your original post. Pull your spark plugs and use a wooden dowel in #1 cylinder to verify beyond a shadow of a doubt that #1 piston is exactly at TDC on the firing stroke within a couple of crank degrees (both intake and exhaust valves closed - might need to pull the valve cover to see for sure). Then confirm that the distributor rotor is exactly lined up with #1 spark pug wire in the dist cap (this is function of the intermediate gear). Once the valve timing is known to be squared away for certain, then you can start to adjust ignition timing.

The business about the engine not running well except at full throttle is a prominent symptom of valve timing being off.