OMG Lisa you are copping everything at once aren't you? First up, get on to a McGrath nurse to help you make those choices like chemo and where to have it. https://www.mcgrathfoundation.com.au/OurMission/OurNurses/FindANurse.aspx?close=y
I was the same as you but I and my 2 kids were a couple of years older when diagnosed. Yep I got the same bombshell, a positive sentinel node and back in to surgery for an axillary clearance. Mate, its not as bad an op as the first one so you have already crossed the hardest part, that mastectomy.
Second thing, you have depression which is very understandable. If you aren't one for medication on that sort of thing, get yourself up and out the door walking. It really is the best medicine although you will be dragging your feet at first. My dogs keep me doing it as they love walkies.
As to chemo, its really not that much of an imposition or as scary as your mind makes out. Its a few hours, probably once every three weeks sitting with a drip thing in your arm. Not that bad. Yes you get some odd side effects and everyone is so different no two ever get the exact same ones but keep up with that walking even if its just to the street intersection and back, it helps.
Nothing really "brave" about treatment, you do what you have to do to survive. You may feel down right now but there is a lower down than that and you don't want to go there. Hang in there Lisa, you got this! <3