I'm a full stack developer and I can't workout how to package my experience

I've got a lot of experience in a lot of different types of development. (I regularly write in Python, JavaScript and C#, and sometimes in Kotlin, Swift, PHP etc... I have never run a big Kafka/Hadoop cluster or some high performance system in akka/erlang. Or writen enough lisp). I'm pro relational database, less so no-sql unless a good fit. I like JSON fields. Prefer redis to speed things up. I've built huge web platforms and worked in almost every frontend framework. Plus about 10 years on and off Unity experience. I run a small agency on my own and get on well with a number of clients. However, it's immensely difficult to get a handle on it all, a lot of the projects I do are "difficult" ie require a range of skillsets that I'd struggle to find a single developer to cover all the bases. I can't work out, what if anything, if I was to try to become "more sensible" what I would restrict myself to in order to stop streching myself so thinnly across so many different technologies and enviroments. My first job for 4-5 years was managing teams of 10-20 as a Technical Project Manager, and I moved into seriously delivering the technology over the last 10. I feel like the answer is to provide a much bulkier up front process (planning / design / ux) in order to grow the value of the work I do, but I've kind of specialised myself in doing the development work as quickly and cost effectively as possible. Obivously that means sometimes there are problems, but in general, as I've delivered so quickly, I'm still about 10x under market rate. And I don't feel it's my world to do design/ux. I have regularly been involved in RapidStarts. ie 2 day hackathons where I delvier a working protype ready for presentation to CEO/CTO level people, and have generally shone in these situations. Working like this is breaking me though, so I'd like to sensibly move to something else or start doing things differently. Perhaps it is just working in a job or working as a day rate contractor? Or selling my business/skills differently. If I was to get a job, what role should I aim for? Any thoughts appreicated!