I think Goku was definitely there. His chi was sensed by everyone around. This could all be an illusion of the Dragonballs, sure, but there's no way to prove that. How could Broly have seen Goku with that gigantic, immense green ball of death in between the huge gap of space between him and Gohan/Goten? I just don't think he could. He acknowledges Goku with his psychopathic "Kakaroto!" AFTER Goku lands and turns Super Saiyan. I doubted for a long time that Broly could sense chi, but, apparently he can. And there's no way he could just SEE Goku, right? With all that chaos going on? Or hear him?
As for Goku being SSj2, that's debatable. Could he? Most likely. Should he? Most likely. Does it definitely look like Gohan turned SSj2 in the final charge? Almost certainly, he was earlier in the movie. Does it look like Goku could have in the final charge? Potentially, but, that could also be attributed to the massive amount of wind that was blowing in their faces.
I however, think that the Kamehameha shot him into the sun for a reason. He tried to erect a chi barrier, and it did momentarily halt the Kamehameha briefly. He yelled in agony/rage when it hit him, but, after that, you don't see him at all until he smashes into the sun. From there, he's screaming and his heart explodes and he is eviscerated. Why send him into the sun otherwise? Because he has healing properties, sure, and maybe to make sure he's defeated and to not leave any doubt in the viewers' mind... but, practically, they had to at least admit there was a good chance he'd survive and that this was their final shot at stopping him, so, they sent him into the sun. I have no doubt in my mind that Kamehameha would have hurt him good, but, damaged him like he was after movie 8? Probably not. Killed him? I'm guessing no. The sun was an insurance policy.
I put M10 Broly at around Good Boo's power level.
Stannis I Baratheon quotes - A Song of Ice and Fire
“I stopped believing in gods the day I saw the Windproud break up across the bay. Any gods so monstrous as to drown my mother and father would never have my worship, I vowed. In King's Landing, the High Septon would prattle at me of how all justice and goodness flowed from the Seven, but all I ever saw of either was made by men."
"Every man shall reap what he has sown, from the highest lord to the lowest gutter rat. And some will lose more than the tips off their fingers, I promise you. They have made my kingdom bleed, and I do not forget that."
"Sacrifice … is never easy, Davos. Or it is no true sacrifice."
“Kings have no friends, only subjects and enemies."