I would agree with your ideas . Most guitar players stop progressing at 35 .Most know the same 50 or so songs at sixty. Learning various styles is the key to progress as well . Learning to play slide in open tunings will also help greatly.Learning to write lyrics and music at a early age is crucial to a solo career .Demo record often to hear your self back will improve your playing . Too many people use back tracks and digital percussion and cannot jam with real musicians .Jam with live people .Practice three to six hours a day or more .Emulate other solos from horns, sax and others .Thanks