There is no ideal size, it depends on your usage. If you install many applications, you'll need a larger root partition. If you save many or large data (documents, images, movies, ...), you'll need a bigger home partition.
If you are unsure, the best is to use a single partition rather than installing a dedicated home partition. Actually on desktop computers using different partitions is often counter productive and you end up facing issues like the one you experienced.
It's a like having a windows system on which everything is installed on the C:\ drive except the user directories that would be on D:\Users... I see you have only 1 ntfs partition so you didn't do that segregation on windows, why do you want to do it on linux ? Also why do you have ext3 partitions and want to format ext2 partitions?