Opinions and suggestions for use of an existing insert.

Shiny black is bad when it comes to creosote. Flaky/ashy is actually less volatile.

What are your heating ambitions?

pen

I'd suggest getting a chimney sweep in there to give the chimney a good cleaning and inspection as well as an inspection of the hearth and surrounding area and stove of course, to ensure it's safety.

Is there a stove collar on the back of the insert that a chimney liner could attach to? If the rest of the setup is safe, and you are only looking to supplement, adding a liner (especially an insulated one) and a fireplace block off plate would increase your safety level.

If this forester has a 6 inch stove collar on it, you'd be golden since that is what the majority of modern stoves use. If that's the case, you could put the liner in now, have the setup inspected by the sweep, and then be ready to simply do a swap to a more efficient unit down the road once you have the cash saved up.

pen