Goku states when he goes SSJB that he's going to use "a little more power" (when I return home tonight I'll get the timestamp).
My take from this comment is that he did not go all out.
The only times he has gone all out, he also uses Kaioken in his SSJB form. Until we see him do so, I'd suggest he's holding back on power.
Edit: He actually says "Let out more power" at 17:38 of Episode 100. This is still useful as "more" is less than "most" or "all".
As to your second question, I'd say that this LSSJ (as was the name for it with Broly, which this is an homage to) transformation, cannot yet to be claimed to be stronger than SSJB. Yes, Kale walked straight through a SSJB Kamehameha, but she was completely taken out by Jiren from Universe 11 - admittedly she wasn't prepared for that hit, but it didn't look like Jiren was trying either. Once we see how Goku fighting serious fares against Jiren fighting serious, we can get an idea of how LSSJ and SSJB stack up.