I think grinding is the best way. If you are replacing the sprocket anyway, grinding the head off of the bolt is easy because you don't need to worry about messing up the sprocket.I tried all the the nuts to see if I could get any to budge. I got a few to spin, but the bolt also spun. And when I put an Allen key on the bolt that just rounded off the bolt head. I ended up grinding the heads off. I wouldn't even recomend anyone try anything other than grinding off the heads, as its seems like a waste of time.
It was 4pm on a Friday and the the replacement bolts would be a special order item (maybe 4 business days wait). So I bought 8.8 steel structural m10 x30mm bolts with nylon locking nuts and red lock tight.($20) Both the nut and the bolt have 17mm heads and the nut doesn't have the metal locking plate that makes it impossible to get off. So in future it should be removable with out too much pain.
New Michelin street 2 tire
Cbr300r sprocket kit 14t/36t
I'm midway through painting the lettering white with acrylic paint
If you are using nylock nuts - you don't need the Locktite. Red Locktite is a bit much for that, and usually requires heat to remove. Nylock nuts alone should be adequate without any (blue) Locktite.
That chain looks kinda taught from the photo. Have you spun the wheel to confirm you made the adjustment at the tightest spot? It may change a lot, and you need to set the slack where it is the tightest.
Having the chain slightly loose is better than slightly tight.