I have a few suggestions for you. I don't think trying to squeeze the stuff you want onto single sided disks is going to be an ideal solution. A lot of software won't work that way (inserting a pause while you put the second disk in). Here's what I would suggest:
You can replace your single sided drive with a double sided drive. The secret here is that old PC 3.5" floppy drives work in the ST. The cabling is identical. You may need to buy cable extenders. And it can be difficult to find a drive that won't involve some cuts to the case.
Buy an Atari ST external drive.
Buy a floppy emulator and replace your disk drive with this. This is the solution I'm going to try very soon on my ST. Look on ebay for "Atari floppy emulator". All your software would go onto a USB memory stick. I have this exact setup on a Commodore Amiga, and it works great. Like I said, as soon as I get some spare time, I want to do this to my ST.
Let us know how you proceed. I'm very interested to know. I'll do the same here when I do the surgery on my ST.