Good news! This is what I found out based on my experience for this trip:

- For any transit/layover above 24 hours at IST, bags will not be checked all the way through to the final destination. Apparently, one will also not be able to go through transfer checks for connection above 24 hours.
- I was able to check my bags in KUL and collect it at ASR (although they were on separate tickets). I think it helped that they were all TK airlines. For the domestic IST-ASR portion, I got the KUL check-in desk to issue a boarding pass to me so that I could show it to the relevant personnel in IST if asked (mobile boarding pass would work too).
- I arrived IST and got to the domestic terminal fairly quick with plenty of time to spare - the boarding gate was not even announced!