Duuuuude! Welcome to the Onebro club! If you can take down Kalameet and Manus Gwynn is no problem. Solid strat on Kalameet, too! I did it the very long, very annoying route of a +15 light crossbow and as many bolts as it could possibly take. That took me a week and the fight itself was probably a solid 15-20 minutes.
lol I forgot I never did Centipede Demon so I had to go all the way to him and beat him but it wasn't too difficult. Now all I need to do is Gwyn which will be no problem. I upgraded the Occult Club to the highest level for lore significance to take down Gwyn but it sucks shit and does no damage so I'm abandoning that strat lol. I thought it was supposed to be super effective against him and it's really not. I can't believe you had the patience for that shit, man.... my Kalameet fight was tough because it was 1 hit kill (which is more or less any boss like that in OneBro) but I was able to beat him in less time than the duration of Power Within. I highly recommend that strat with Power Within stacked on top of RTSR
And yeah, KenOh, I've seen for the one move that's in my video, it just takes 3 quick taps of that to deflect it all and give you time to cool down and dodge a follow up attack. I highly recommend the glass canon danger strat of RTSR and Power Within if you have the Sanctus. It made Manus and Kalameet pretty fucking easy and seeing 1018 HP damage to Manus with one Great Fireball made that fight way more empowering and seemingly possible than just slowly ticking away his health little by little. The only annoying part is figuring out a way to get to a good HP count to activate Power Within and Sanctus...important to note that walking through a fog gate stops the HP drain of Power Within but not Sanctus regen and could lead to you fighting Manus with Sanctus on and bringing your HP up to a spot where it de-activates RTSR buff.