I had to wean off formula top ups as my baby had been exclusively tube + bottle fed during her 3 week stay in Nicu (part formula part expressed milk). I didn't start bf at all until she was 2 weeks old, though I'd been pumping. It took a week or so once we were home to wean off formula top ups. It can be done, it is 100% not too late.
First thing to say is don't get hung up on how much you can pump, it doesn't correlate that closely with how much your baby can get and it's possible for most women to increase supply quite quickly through on demand feeding.
The most important thing is to feed, feed, feed. This will build up your supply. If you can, set aside the next few days and stay in bed/in front of the TV with tonnes of snacks. Feed on demand. Expect intense periods of cluster feeding for the first couple of weeks, which can be painful and wearisome, I used nipple shields for a time. It's supply and demand so the more you feed the more milk you'll produce. You need to drink more water than you can imagine and stay fuelled.
If you are worried your baby isn't getting enough, the single most important thing to monitor is dirty/wet nappies. If you can, get your baby weighed every 2-3 days.
I planned to taper top ups by 10mls per feed per day, but I ended up not doing it in such a structured way as sometimes she fed to sleep or wouldn't take the top up.
I was then actually able to stop the top ups within less than a week as I could see she was satisfied, there were plenty of wet nappies and she was gaining weight. So having planned to gradually taper to nothing I ended up going cold turkey halfway through and it was fine.
Be prepared, it's an intense period when you are feeding to build supply like this, you will feel like you do nothing but feed, but it didn't last long and it was worth it because apart from anything else the top ups were such a faff.
I found the kelly mom website useful,the advice you have had from professionals so far seems a bit mediocre so it may be worth trying a breastfeeding support group or specialist advice service. Good luck!