Consult a mechanic on 1 and 2. Without hearing the engine it's too difficult to tell. I thought my '99 was a little noisy until I heard a few others. They all sound the same; a little clickity clackity. It's normal. But if it really is knocking then it needs to be looked at.

As for 3, I believe the TL (or some Acura) sway bar can be installed on a 6th gen Accord, but I don't know. It's been covered on this forum before. Use the search bar.

As for 4, seafoam can be used in the gas tank to clean injectors and fuel lines, in the oil to clean your internals up or through the PVC valve to clean your manifold and fuel injectors up. Read the instructions on the bottle. Use it just like it says. Alot of guys swear by the stuff. I've used it with minimal change but I don't think my car really needed it. Again, been covered on the forum. Use the search bar.

For 5, 110,000 Kilometers is about 70,000 miles. The timing belt should be changed at 105,000 miles for the 6th gen accord so you have a while yet. There really are no noticable changes when you get your timing belt chaged, or at least there shouldn't be. It's just simply replacing the belt so it doesn't snap and destroy your engine via bent valves. I'd recommend going to the dealership for it so your covered if something goes wrong. They will opt to replace a few other things like the water pump and belt tensioner. But it's a waste to do it before the 105K miles mark.

For the list of items you mentioned you have done, all sound good except for the transmission flush. Assuming you have an automatic transmission, never get it flushed. At least not the flush that most tranny shops do. Those "power" flushes will wipe a 6th gen honda tranny out. Though they fixed most of the quirks (carrier bearings) in the transmissions by 2002, honda's archilles heel has been it's automatic transmission for at least the last decade. Be easy on it. Only used authentic honda auto tranny fluid and only change it via draining and replacing. If your tranny is manual then you don't have much to worry about. Use honda authetic manual tranny fluid for that. I think most of the SE's were auto's though. Good luck!