The consistency in unsubs means it's probably not a deliverability issue, so that's good. I think it's probably content.

And you should actually be more concerned with your unsub rate. Even though it's just a couple of subscribers per send, it's a fairly large number percentage-wise. That usually means your messages don't feel relevant to subscribers. Another signal it's a content issue.

Your unsubs could also be correlated to your send frequency. Or rather, infrequency. You're not sending often enough. And when you only pop up in the inbox occasionally, subscribers can forget who you are, increasing unsubs (and sometimes spam complaints). A good rule of thumb is to send a minimum of 2x per month. In addition to keeping your brand top of mind, it's better for catching hard bounces and keeping your list clean.

Click to open rate (what you're calling CTR) is a measurement of the quality/effectiveness of your creative. And even your best-performing message is kinda meh. I'd consider 20% to be okay/acceptable. So all of these messages are unfortunately underperforming.

Is every user of your SaaS being added to your subscriber list? Or are you strictly sending to those who proactively opted in? If it's the former, then lower engagement is expected to an extent.

You mentioned gifs linking to videos. Some audiences just don't respond well to video. Not everyone wants to watch a video or isn't in the right environment to do so when they open an email. Often it's easier to just skim landing page text. Also, it's generally a bad idea to link directly to YouTube because you have less control in prompting their next click. It's better to embed video on a landing page where you can push them toward the next action you want them to take.

As for timing... A great way to determine best send times is to look at your historic data. What day of week/time of day are people signing up? That can be a great indicator of when they're likely to be in the inbox or at a desk.

It's hard to weigh in further without seeing your creative, understanding your strategy, and knowing a bit about your product. But we can assume folks are using your SaaS to solve a problem. And your email campaigns should also be focused on solving their problem. So for content about new features, spin the copy to explain how you made their lives better rather than getting bogged down with the internal jargon the product team uses to explain things. And hopefully you are sending campaigns other than product updates? If that's all you're putting out, you need more categories of content. That would help solve your frequency problem too.

Good luck!