First, you can exceed the 1000 character limit by editing your post.

1.) Bio and Virus function very differently. Bio is an attack spell part of the ARC/SMN rotation designed to do damage; as such, it uses a GCD. Virus is an off GCD mitigation tool designed to weaken incoming damage, it has a much longer recast timer and is designed to be used as soon as big moves are being used; as such it is OGCD so that you aren't stuck waiting for the GCD to use it when it is needed.

2.) You get more used to the tab targetting system the more you do it it's all about the way you angle your camera. Alternatively, it can be quicker to switch targets from the enemy list, particularly in trials where you need to change to a specific add. If you're playing on one of the Playstation platforms you can still change target based off of the enemy list by holding L1 and using up and down on the D-pad.

3.) A minor inconvenience at worst. I'm used to just dismounting already anytime I want to talk to someone. No idea why this is.

4.) All of the major/reoccuring debuffs that I can think of are typically red with a white image in the middle. If there are special debuffs in an encounter, you'll just have to learn them. Again, the more you play and get used to the different symbols, the easier they are to pick out.

5.) Do you mean in your retainers or in your actual armory inventory? In your retainers, you can sort only so that all like inventory is grouped together bodies, hands, waists, legs etc. In the armory inventory everything you can't use should be grayed out as you stated.

6.) Each levehest giver is their own unique entity. The leves you get in town are not the same leves as the ones you get in the field towns. In the same vein it'd be odd if I finished a quest and took the results to someone else who was mildly related. With aetherites though, travelling is incredibly easy so getting back to town to turn the leve in and then teleporting back to the same town you were in shouldn't be much of a problem save for a few cases.

7.) If you want to change you channel instead of typing "/p Hello! (auto-translated)." and then hitting enter, type "/p" hit enter "Hello! (auto-translated)". By typing /p then hitting enter it changes your current channel. /p, /l1-/l8 for linkshells, /s for say, /sh for shout, /fc for FC, etc.

I hope some of that helped. A lot of it you just get used to the more you experience it.