My main issue is that I work in Python, mostly on web based stuff, so the lack of Java/C# cuts a lot of jobs in half

Is that what you're seeing the wild for remote positions? My intuition had me thinking that Java/C# is more prominent in "enterprisy"-type companies where telecommuting is less common. In my anecdotal experience, the companies who welcome telecommuting the most, also tend to be more progressive with their technology usage. I feel like Python+Web should be a fairly ideal combination for remote work. If you were intent on being an embedded C programmer, for instance, it might be a little more difficult due to the nature of the job.

Either way, I'm curious what the proportion of telecommuting jobs to non there are

Based on observations and discussions with other developers, I expect most prefer to work in an office and live in the big city, so the jobs are apt to reflect that anyway. I'm not sure it works that well financially, but I definitely see the appeal of that life for other reasons, which cannot be discounted. Lots of tradeoffs to consider. Something you, being a developer, will understand very well I am sure.

I worry about flexibility since I really don't want to get stuck in a dull Java job that drives me insane.

If it eases your mind, I have never written Java or C# professionally.

I was actually noting to someone the other day about how my current job, eerily, seems to follow my personal interests around. I have actually encountered looking at a random problem on a weekend just for my own curiosity with no connection to anything I do professionally, and that following week saw new requirements to solve that exact problem.

I find my job pretty exciting. I'm sure there are a lot of dull ones to be had, but I don't think the method of how you get to work changes that. I know a few people who do find their work dull and have to go to the office.