You have two options:

1. Compress the video using something like Handbrake. It won't look as good but you can give it a test pass to see what it looks like
2. Buy DVD 9 Double layer discs that will actually fit the contents

Suprise 3rd option: Split the ISO over multiple discs /s

There's a utility called DVDShrink which will reencode a video DVD-9 to DVD-5. It's old, but I think it still works.

Have you thought about just putting the episodes on a thumb drive instead? Most things that can play DVD/BD can play videos from a USB.

Normal DVD-R max out at 4.7GB. Wikipedia says there are double layer recordable DVDs with 8.5 GB, I've just never seen one of them. But they're available on Amazon.

Idk. I usually just copy files onto USB thumbdrives these days.

Do they need to play on a set top DVD player? If they are going to be played on a computer, you can reencode to a modern codec and burn them as data DVDs.

You can split them and just have twice as many disks, bit of work though

How necessary are the DVDs? Could share them peer to peer over something like soulseek, or set up an sftp server, or a shared drive accessed via Tailscale?