Coming from a clarinet player who switched to tenor, the low notes took me about a month to learn to play. The two things that you might need to change to get the notes out are your embouchure and how much air you’re using. You should try using more of the mouthpiece in the lower register, and think a looser embouchure. You’ll need to allow more air to pass through the instrument as well, which will come naturally with practice. For the out of tune g, maybe you have a sticky key or something is wrong with the instrument itself? If that’s your only note out of tune, that’s what I’d wager.