Poolpatient, welcome to the forum. I realise this post is a little old, but I've got an idea that might work well for you. As you seem to have high alk fill water, is there any way you could 'pretreat' the fill water (acid and airation) before adding it to the pool? What I'm thinking about is a 55 gal plastic container - put a little of the fill water in it and add some acid (you're adding it bi-weekly anyway) and let the water bubble and splash (airation) as the container fills - I'm thinking that this will knock the alk of the fill water down before it enters the pool, reducing the amount of acid required (it takes less to treat 55 gal than 15,000, you'll also have really low pH for some of the filling which should increase the alk lowering. I don't know if this would be practical for you, but thought I'd offer the suggestion.
If you're happy with the way you've been doing things, keep doing it the way you have been. Again, welcome to the forum - Waste

ps. RE: calcium and SWCGs - liner pools don't need cal, they don't mind it, but don't need it. However, the manufacturers reccomend 200+ ppm (the 'stumper' is that most units switch polarity regularly to remove any calcium buildup on the plates, so they obviously don't want it there - yet they tell you to add cal to a pool that doesn't need it ) (If anyone has thoughts on my suggestion or my SWCG observation, please post, I'd love to hear from the pros! THX)