Nice! (for everyone except island residents)Sweden. All power companies except the island of Gotland is required to accept solar installations. Energy meters installed can already measure power in both directions.
You wouldn't split the pack. Two can be run in parallel off the same pack. I believe they support up to 4 running networked together.The Schneider XW pro 6848 did mention both dumb lithium, lead acid and two-stage charging curve so seems very DIY friendly. I did not however find whether it could export from battery to grid, and 6.8 kW is small so I would need two. Pros and cons of splitting the battery pack in half for each.
It has a web portal with about 1 bazillion settings if you can do time based sell to grid, but it sounds like you'd need to change the schedule almost daily.How do you do when you sell from battery to grid with yours? Can you set it via Ethernet, WiFi, RS-232 or similar?
I control it via Modbus over TCP/IP (ethernet) with a raspberry pi. Another member here controls his via a small industrial PLC.