120,000 mile service and maintenance questions

Greetings,

I hope you all had an enjoyable Memorial Day weekend. I am coming up on 120k miles before the end of the year (put 7,500 on my used Prius in the first 5 months, and we are hardly into the summer where travel, day trips, and graduations/weddings/parties mean even more use of the car).

I know many of you would say "follow the maintenance schedule," but I have a few nagging things that might need more immediate attention:

1. Clanging/banging noise from the front end when I turn when stopped. It's sounding like struts or strut mounts, but it doesn't do it when in motion (or as loudly), so I was just thinking of DIY replacing the entire front struts with KYBs, unless it's a bad idea to just throw parts at it (car has almost 110k miles, even if it doesn't fix the issue, I'd say it might be worth it?) Any ideas what else could cause this?

2. Brake pedal cover worn out. I think I can easily DIY replace this myself, considering some options that may be a little less slippery since I do drive this car in the winter.

3. Some trim pieces are coming apart, causing water to enter my driver's side door. I think this is part of the reason for #4, which I'd like to do immediately.

4. I can barely hear a phone call on Bluetooth, and all the low-mid frequencies are distorted. I know I have a bad driver side speaker, but would assume the tweeters on the dash and the right speaker could still carry the rest of the frequencies for a semi-clear conversation. Would like to replace with these woofers (for a more hi-fi sound), any issues with them not being a "direct fit"? The impedance, size, and wattage should be close to the OE speakers and not cause problems: C 165 - Hertz car audio systems | The Sound Experience

5. Car started doing "HV Battery low" warning on extremely hot days when parked outside. I'm thinking I have a bad 12V, but if (at 107,000 miles and 9.5 years) the HV battery is going dead, what are my options? Used pack? Greentec? Had a really bad experience with a reman HV battery ($10+k) on my GM hybrid, the OEM battery had much better cell balance and reliability.

6. My entire dash rattles when the ICE starts up, I feel like I have a rough-running ICE compared to other HV and PHEV vehicles I've driven. Motor mounts? Spark plugs? As far as I know, all of those are original.

7. Maintenance. I want to go through everything myself (coolant flush, trans fluid exchange, plugs, inverter coolant, etc.) but am afraid I will cause more problems (especially after I had an inverter warning code post inverter coolant flush on my 2012 Volt). What fluids and items can I reasonably DIY without wrecking the car? I hate putting in the effort on a used car just to be told by a trans shop, "you should've left it alone". Are there any filters I should easily do? AFAIK, most of those are likely original on my car (same for the 12V battery, it has a 2017 date code).

Thank you for reading this long-winded post; #1, #2, and #5 are giving me some fear since I drive this car 2 hours daily, but #3, #4, and #7 are things I would like to tackle first - since I plan to DIY most or all of the repairs (going to a shop these days is just too expensive!) to improve my car's reliability.

FWIW - my skill level is: Have done major suspension work (ball joints, control arms) and drivetrain work (CV joints), but am afraid of internal component rebuilding (transmission, engine, etc.) including things like replacing timing chains and torque converters. I can turn a wrench but am not a pro.