My physics teacher was vague on the mass to energy conversion in chemical reactions. You have made at least 10 times as much sense as old "what's-'is-name".
Would the mass loss in a nuclear reaction be compensated in the relativistic way by the high speed of the resultant particles?
I'm not sure what you mean exactly. It is true that part of the mass loss is in the kinetic energy of flight of the particles -- but that particle could hit something and come to a dead stop, of course, and the mass loss of the original nuclear reaction is still the same.