Ok the best way to tell if fermentation is complete is via a SG reading. Basically take a sample (sanitize 1st) and recording the SG and then wait 48 hours and check and then 48 hours after that another test. If all three are the same then fermentation has completed. I normally wait 21 days before I take the 1st test. I only use secondary for lagers and simply add pumpkin directly to the primary. as in:
https://www.homebrewtalk.com/f12/how-much-pumpkin-needed-pumpkin-ale-435678/index2.html
1/2 cup brown sugar is not going to make it to sweet and it could restart fermentation. All table sugars (cane, white, brown) are basically sucrose the simplest sugars and yeast will eat them up fast since they can break then down easily. Brown sugar has molasses and will leave a flavor in the beer ( a good one in this case) ... I use fresh pumpkin in the mash and canned in the last part of fermentation.
what was the SG after you chilled it and pitched the yeast and did you take a SG when you put it in secondary.
The pumpkin may sink after soaking a while but if it doesn't that will not matter. You will still get some flavor from it. Need the SG readings to really know what to do next.