Your rules for consecrated ground are stronger than the DMG's rules for desecrated ground
Firstly, I like the disadvantage on saving throws for undead; this mirrors the rules for desecrated ground. An alternative could have been that celestials get advantage, but I wouldn't have both together since desecrated ground only has one (advantage for undead and not disadvantage for anyone).
However, the 1d6 radiant damage is very strong, especially against undead (consider zombies, which die without getting to use their Undead Fortitude if they take radiant damage, and of course vampires, which cannot regenerate health). The rules for desecrated ground doesn't have anything nearly this strong. Not even the hallow spell does consistent damage like this.
I know you said you wanted to mirror the DMG description of holy water purifying desecrated ground, but its not like there are going to be puddles of it all over the floor. There's not really much justification as to why consecrated ground would have an effect this strong.
As for your addition to desecrated ground to balance things out, celestials using Healing Touch less efficiently is simply too situational to really balance things out. Especially in the Curse of Strahd adventure, this only affects precisely one NPC, who probably isn't going to be near any desecrated ground anyway.
If you are going to introduce rules for consecrated ground, I'd stick to just the disadvantage to saving throws part and nothing else.
For Curse of Strahd specifically, I don't think it's a good fit
The Church of St. Andral in Vallaki, pp. 97-98, I think is a poor choice for this effect. It will only really matter if you use the "St. Andral's Feast" Special Event from p. 124, where vampire spawn and Strahd himself attack the chapel, before restoring the bones and thus activating a hallow spell.
Based on my own experience with running this Special Event (so this is all anecdotal and therefore subject to personal tastes and opinions of how one "should" run Curse of Strahd), this attack is supposed to be a scary moment; suddenly, all these vampire spawn burst out and start attacking the chapel, and as the party try to defend themselves and the chapel, Strahd himself turns up and tries to kill the priest!
In my game, I have some town guard join in, who were also there to "keep the vampire spawn busy" once the party had spotted Strahd and decided to break away from the fight outside with the vampire spawn to try to save the priest. Remember, at the beginning of the book, it says this about Strahd (at the end of p. 10):
These encounters are meant to test the characters, not kill them. After a few rounds of toying with them, Strahd and his creatures withdraw. If the characters retreat, Strahd is likely to allow them to flee, savoring their fear and believing he has broken them.
In my case, once Strahd had taken a couple of swings at the priest and fought the party, he managed to drop one to 0 HP and then laughed at them and fled, leaving the priest alive. Had the party not have intervened, though, I'd have let Strahd kill the priest.
The vampire spawn kept attacking the guards in my case, so that the party could heal their downed member and at least finish the vampire spawn off (with the guards' help) so that the party felt like they at least managed to safe the chapel, but at the same time was still a scary encounter and still makes Strahd out to be very powerful, and that they were lucky to get away from him alive.
If this were consecrated ground using your rules, then the vampire spawn and Strahd would all be taking constant damage and probably trying to get away, which would undermine the attack and the scariness of the event. They would also have disadvantage on any saving throws against Turn Undead or any spells.
Also, although you wanted a "cinematic moment" of zombies and vampires bursting into flames, but that's not really what Curse of Strahd is about; it's about gothic horror, where the people live in misery because there are no safe places, and where the threat of Strahd turning up and ruining peoples' day is a real possibility at any moment. To have a "safe place" I feel undermines that, since the party should never feel completely safe.
I don't think it would necessarily "disrupt any plot points", but it would undermine this encounter. I suggest leaving this as non-consecrated ground and have the battle play out.