Can't run Captive emulation

I find that the blinking cursor issue goes away when you choose EGA instead of VGA as the game is starting ("Please select your video mode" > 2). The game also feels a lot smoother. I'm not sure how frequent your freezing was, but I didn't see any freezing in either mode in the ~10 minutes I was in the game. However, since EGA was a lot smoother, it may fix the freezing as well.

I tested this on a windows machine, as well as a browser - based dosbox (here), so I can't say for sure what effect Linux will have. But if the freezing still crashes in the installed version of dosbox, I'd recommend you try the online version.

P.S. - I selected option 1 (Sound Blaster) for both sound questions at startup.

EDIT: Adding screenshots in VGA and EGA to compare. VGA

EGA