Yes the J shape is supposed to be there for expansion. If you look at a Diablo blade it has the J relief cuts at the edges and also d-shaped relief cuts within the body of the blade. The large tooth looks like it may be build up of aluminum on the carbide tooth. It definitely doesn't look like carbide. If it is Aluminum it should be easy to pull off with a pair of needle-nose pliers. Aluminum is really good at gumming up blades. I'm pretty sure they actually make blades that are specific to aluminum to avoid the gumming up issue.
Here's an example of an aluminum blade
From the website
Diablo's next generation Aluminum saw blades are optimized for cutting thin (up to 1/8”), medium (3/32”-1/4”) and thick (3/16”-7/16”) aluminum metals. Featuring the new, specially formulated Diablo TiCo™ Super-Density Micro-Grain Carbide, these radical blades withstand impact, reduce wear, provide clog free cuts and last longer than standard carbide in metal cutting applications. The specially formulated metal cutting carbide teeth feature a Triple Chip Grind (TCG) Tooth Design for clean, burr-free finishes, virtually eliminating any type of rework. Tri-Metal Shock Resistant Brazing allows these Aluminum blades to slice through metal materials while withstanding extreme impact for maximum durability. Diablo's Aluminum saw blade series is ideal for corded and cordless saws when on-the-job cutting non-ferrous metals such as aluminum extrusions, copper pipe, brass plate, etc.