How to format an SD card to fat32 with custom Allocation Block Size
To format a disk with custom (FAT) allocation block sizes use the -c option with e.g. sudo newfs_msdos -F 12|16|32 diskXsY. -F is the FAT type (usually FAT32 here).

First get the disk identifier with diskutil list and the block size of the disk with diskutil info diskYsX | grep "Device Block Size".

To get the -c factor divide the wanted allocation block size by the device block size: e.g. 65536/4096 = 16. Acceptable values are powers of 2 in the range 1 through 128.

Assuming the device block size is 512 Bytes in your case, the factor is 65536/512 = 128 and the resulting command is:

diskutil umount disXsY
sudo newfs_msdos -F 32 -c 128 diskXsY


An additional -v name option will also add a name for the volume.