musictheory.net provides the ability to make custom web exercises to practice music theory topics. I have created several buttons below for custom exercises for CLARINET players. Please be aware that you will need these exact links to get the exact exercises you need.
I recommend that clarinet players not only try another size of clarinet, but also consider learning the basics of flute and/or saxophone. In pit orchestras and jazz bands, clarinet players are sometimes required to switch back and forth between multiple instruments. I have been selected for paying gigs because of my ability to play more than just clarinet.
After learning flute and saxophone, it is OK to learn double reeds like oboe and bassoon, but those are only necessary in some pit orchestras. I do not play oboe or bassoon because they are only very rarely used in jazz. Unless you are asked to learn a double reed for a concert band, I would recommend learning flute and saxophone first.