This has to be bait but I'll bite.
1: SCH is the only healer with an always available, instant cast DPS skill that isn't a DoT. SCH also has plenty of oGCD heals so you can heal on the move without letting your GCD halt entirely.
2: I have no idea what you mean by this.
3: Mana regen doesn't seem any worse than Endwalker, where it was absolutely fine? If you're abusing Seraphism and spamming out heals, yes, you'll go out of mana.. but you're not meant to GCD heal back to back to back.
4: SCH already has tools for healing yourself up if you res smartly. Ruin II > Aetherflow > Emergency Tactics > Adlo. Summon > Dissipate > Adlo > Lustrate. Adlo > Physick > [pray for forgiveness]. What tools do the other healers have that Scholar lacks? White Mage has Benediction, which you SHOULD NOT be using on yourself, but I see far too many healers do it after they die. Astro has ED? Which isn't even that strong? And what does Sage have?
As for your suggestion: SCH does not need low level buffs.
5: I agree that SCH has anti-synergy, and that is something I complain about too. Your examples aren't that great, though?
a) Skills being cancelled is an issue that should be addressed, yes. Not being able to use aetherpact is a choice between AoE and single target healing, Seraph is for AoE.
b) Losing access to skills is, on its own, fine. You get a big resource drop as a tradeoff. The actual issue is that Dissipation doesn't buff your oGCDs, nor do your oGCDs generate gauge for Aetherpact, so the skill encourages you to use tools intuitively while unintuitively not buffing them or outright nerfing their utility. Fix the buff not applying to abilities and fix it not giving Fey Gauge.
c) Why are you GCD healing that much, and how are you running out of mana after only 3 or 4 casts? This is a skill issue, not an ability issue.
6: Ruin II is 220 potency. White Mage only has Dia, which is 70 and overwrites your DoT. Astrologian only has Combust III, which deals NO instant damage and overwrites your DoT. Sage only has Eukrasian Dosis III, which deals NO instant damage, overwrites your DoT, and because it requires using two skills, can also be prone to causing weaving issues if you have high ping. Every other skill that the other three healers have that are DPS neutral or a DPS gain with no cast time are conditional procs or on cooldowns. Scholar has the best reliable mobile DPS of all four healers.
7: 15 yalms is fine. CBU3 constantly buffing the range of everything is making players lazier.
8: Your reward for using Adlo and Succor is not dying, and the lack of reward for using them is your punishment for needing to GCD heal.
The only change I want is for them to let us turn off Seraphism's forced glam override.