Constant hissing sounds from water heater, WH kettling sounds & pilot light repeatedly extinguishing after showers, rusty WH flue pipe & dripping sounds in flue when it rains, and sweet smokey smell from air vents when heat kicks on, help! (see imgur links)

This is a gas water heater and gas furnace question.

imgur links: https://imgur.com/a/HqMkp38

https://imgur.com/a/tqxRq9s

My parents had a new furnace and a water heater installed by an HVAC. Unfortunately now we are having a lot of issues. I suspect a lot (if not most) of the old ductwork is done by a family friend (not an HVAC pro). We brought up the issues to the company that installed the water heater & furnace, and they were really dismissive. (We've also already had 3-4 different gas leaks found/repaired so I wouldn't be surprised if there were more.) I am planning to call out a different company to come check it out, but I was wondering if there were any specific things that could be causing these issues/ glaring issues that stick out based on my pictures & videos just so I can be prepared. Thanks!