Errrrrr.... WHY?
The limits you describe are correct... for the tmpfs mount itself! They will not apply to whatever you store inside the sdcard mountpoint. If you let the default mountpoint, then your changes simplify quite a lot: you just need to bind mount the Android sdcard directory, and that's about it.
[root@localhost nemo]# mount -o bind /run/user/100000/media/sdcard /home/nemo [root@localhost nemo]# mount -o bind /run/user/100000/media/sdcard /data/sdcard
[root@localhost nemo]# df -h Filesystem Size Used Avail Use% Mounted on rootfs 14G 4.1G 9.2G 31% / /dev/mmcblk0p28 14G 4.1G 9.2G 31% / devtmpfs 406M 64K 406M 1% /dev tmpfs 407M 72K 407M 1% /dev/shm tmpfs 407M 33M 374M 9% /run tmpfs 407M 0 407M 0% /sys/fs/cgroup tmpfs 407M 8.0K 407M 1% /tmp /dev/mmcblk0p25 8.0M 4.2M 3.8M 54% /persist /dev/mmcblk0p19 8.0M 4.1M 3.9M 52% /drm /dev/mmcblk0p9 48M 7.1M 41M 15% /var/systemlog /dev/mmcblk0p18 64M 45M 20M 70% /firmware /dev/mmcblk0p28 14G 4.1G 9.2G 31% /swap /dev/mmcblk0p28 14G 4.1G 9.2G 31% /home tmpfs 407M 0 407M 0% /mnt/asec tmpfs 407M 0 407M 0% /mnt/obb tmpfs 407M 33M 374M 9% /home/nemo tmpfs 407M 33M 374M 9% /data/sdcard