I wouldn't bother to add the cya yet, because you will be having to backwash and vacuum to waste a lot, and the chlorine will be more effective with a low cya. You must keep your chlorine levels at least at 10, I would even go a little higher,. You will have to add chlorine to get you up to 10 at least 3 x a day. It takes a lot of chlorine to get rid of all the baquacil left over in the pool, and you have to keep your filter running 24/7. Once you can hold a chlorine level overnight, then you are getting close to the end. When you can start to hold chlorine (you ewill not hold it in the day because with the low cya the sun will eat the chlorine, that's why it's necessary to check the level in the middle of the day too.), you can then add the stabilizer. Put it in an old nylon sock and tie it ito the ladder of the pool - it can be added in the skimmer, but you can't backwash for at least a week after adding it through the skimmer, so you will have to add it to the pool - it dissolves slowly, so you have to have it in something to contain it to one place (the stocking) because you will still have lots of fall out from the conversion and will need to vacuum to waste. Once the water is crystal clear, and it will be!!, then you will need to change the sand in your filter - the orange that is coming out of the backwash is the stuff that is gumming up your filter, which is normal after a baquacil conversion. Just keep adding bleach - the more bleach you add the faster the conversion will be. I did the conversion on my fiberglass pool also. You are on the right track, just add the alk up, if you didn't buy it yet, you can just add regular baking soda - that is all that alkalinity up is, but you pay more for it at the pool store. Don't take your ph above 7.0 to 7.2 for now, until you can bring your chlorine levels back down to normal, you can get staining in a fiberglass pool, which can also be removed, but keeping the ph low for now will be better. So don't add more alk up untill you test again and post the numbers. You can go to the Pool Solutions site and read up on swimming pool tips, it will give you a lot of great information. Here is a table of the best guess chlorine chart is to maintaining chlorine:
tabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

Feel free to ask any questions. I know it's hard, but the patience will pay off in the end, and running a chlorine pool is much easier, and much cheaper!!. When I put my fiberglasss pool in 7 years ago, they started me on baquacil too, and I switched the following year, because of the hassle and cost.