Doraemon should be 9-A. Nobita withstood tank shells from the invisible tank Doraemon gave to Suneo, which caused human sized craters. Suneo withstood Gian's explosion after the anger suppression gadget overloaded him. The explosion left a pretty good crater. Doraemon can harm them
I'm very sceptical about anime feats, adapting from the manga or original, because they tend to play out for dramatic effects or expand on the source material. The manga only gives us some human-sized explosions. I can't calc those explosion, but they likely won't yield anything close to 9-A. Also withstanding is a bit overstating it. Whoever took those explosions are out for the count, unlike Wang Dora's feat (which robot cats scale from) after which he kept fighting.
TL;DR: I'm somewhat against using those explosion feats to upgrade the verse. If they yield similar results to the Wang Dora feat, no problem. But if they are too high, we have to take them being outliers into consideration. Otherwise I'd have brought up this 9-A Dora-Rinho feat a long time ago.
Giving 9-B to non-robot characters is already unusual because it inflates the verse
I can't seem to find any feats in the links (my antivirus flagged the scan link). For the boulder feat, since it looks fragmented, it'd need a radius of around 86cm or about 3.8 footballs to be 9-A. Since it's not obvious by eyeballing, given that info, you should ask someone to calc that.