A lot of this got covered in the sorclock thread, but:
1) Level 2 rituals are fine. They're even cheaper if you can convince your own party members to teach you them. It can be out of character for them to do so, although I'd expect Archfey bardlocks get along fine with druids and nature clerics, and valour bardlocks with war/tempest. Lore bards would have similar goals to Knowledge clerics, and Death and fiends tend to get along ok too. You may even worship the same god/power as them, even if you're not an actual cleric or druid. Or it could be a ruse to plunder their knowledge. Anyway, there's plenty of cool lvl1/2 rituals to learn, and there's enough ways of getting them with a bit of RP work or collaboration.
2) Chainlock actually "kind of" got a buff to the familiar. Putting attacks into the REaction timing frees up the familiar's normal action for all the other stuff they usually do. Invis/use or throw items/help/change forms/dash mainly. They're like tiny little invisible rogues, just without the SA damage. It's a different action economy, but there's a good case to be made that it's a "better" one than before. More-so as a valour bard.
3) You get hex and eblast from lock. But you also get all kinds of other stuff. Tome cantrips/a snazzy familiar, some pact spells, an invocation, a couple of level 2 slots to burn off into sorcery points every encounter (one really, mostly hex gets used on the other). It gives plenty of free resources that you don't get with just bardsorc alone. Is it better than level 9 spells? Might be, but probably not. Potentially more sustainable, and about as versatile though. It's a flavour choice and a campaign choice. If your campaign sort of ends before lvl 20, then who knows which one is better.
Anyway, I'll throw together a build later on today and see how it turns out. I'll probably leave sorc 3 until the end of the build. Just consider it your capstone (metamagic and the font IS a good capstone for any sort of caster). Still undecided on Bard 15/Lock 2 or Bard 14/Lock 3 though. Probably the latter, just so I don't make my own arguments moot.