Yep, 1TB should be fine for a HDD, although you can probably get 2 or larger for only a small price increase. HDD storage is very inexpensive anymore.
On the SSD, I'd suggest a minimum of 256 GB. There are differing schools of thought on whether one should have all the music stuff live on the SSD or whether to use it only for the OS and system files and use the HDD for everything else. Personally I am in the former school, because that's how you realize the massive speed gain from using the SSD in the first place. A great example are VSTi plugs that have large libraries. If your system has to go get those files from the HDD instead of the SSD, you will get much less improvement in performance. (In my experience nothing speeds up a computer more than running off a SSD, it's not close.)
On my rig, I have a 512GB SSD and with Windows, web browser, anti-malware, my DAW and all plugins/libraries, and MS Office installed, I still have over 200 gigs free at any given time. That's ample for me.
So my SOP is to drive everything from the SSD and then every so often transfer the folders containing finished projects over to the HDD for archiving. My stuff is similar in scope to yours -- 30 tracks is a normal max for me, often a lot fewer -- and by the time a project is done its folder is many gigs in size. Doing this is good standard practice anyway for backing up one's work.
Other folks just don't want to be bothered having to do that, and I can understand that. But for me it's a trivial investment in effort for a huge payoff in performance.