1. A knok, preferably improved on a build that can deliver -8disc on target while having relevant AB is essential.
(Not to mention TS + -8, and no, you can't always outrun a TS, especially in a mess and/or lag).
2. In a build that focuses on more then two stats losing one gear slot is detrimental. Don't forget that helm/armor is usually 1 stat max.
Usually that extra slot means more even cont that on lvl 30 will give +30hp that will replace toughness.
Lets not forget that unless you use pots only, cont buff is unreliable due to mords etc.
3. still spell vs extra epic feat? Somewhat depends on your gear.
https://nwn.fandom.com/wiki/Bard_song = see how much perform you need to get -8. Usually song comes before curse allowing less actual
perform to net 50. Make sure you have 50 even after cha buff is potentially dispelled.
Calculate your saves with gear on test server. Make sure you have enough extra disc(from gear) NOT under song.
Same with perform and even a bit spellcraft if it fits to gain a bit more saves.
Calculate how much gold you will need to get that gear, and if you think you can(want) to get enough 3 lvl runes to have relevant maxed gear.
You do need 40fort, and relevant will(especially now, yes you have fear pal, still).
40 fort, ~60 disc(presong), ~35+will, calculate perform song+cha.
Considering above maybe you will see a value in esf.disc or es.fort.
Prowless/imp.knok is a matter of min/maxer taste with full costly gear+pots.
4. Ethereal visage is high in the breach list, meaning it will be gone after one lesser breach. I do recommend the sr helm.
5. While both approaches are valuable, I personally believe heal+more.umd(+1ab,blind,etc)+point 3 > conc+still.
Yes sonic shield is great. Unfortunately netting you a 20 caster lvl on the spot. You want +2ab? Squeeze the ball for 9 rounds.
Of course the above is an imho, and since I don't have the mighty badge(lol without a doubt, just lol...) you don't have to take it seriously -).
p.c Don't forget bards have a cheat harp in carpentry and another lesser cheat harp.