At level one we can expect this ability to be dealing around 2d4+6 damage. without calculating for accuracy that’s an average of 12 damage, compared to the DMGs spell creation guide a first level spell should be dealing 2d10 damage (average 12). While this ability does require the use of your bonus action which would be a value increase it is offset slightly by the requirement that it is used on the same turn as the attack action.

While this is a powerful ability, when compared to the defensive capability one can get with a 1st level spell slot this pales. For this we are comparing it to the shield spell. Patient defense is used as a bonus action and not a reaction making it less valuable, additionally we can calculate the average roll adjustment by disadvantage as about 3.4 (this article does a good job of explaining). Of course 3 is less than 5 making this ability absolutely not worth a 1st level spell slot

Escaping from a melee is highly valuable to characters with low health, it’s one reason misty step is a common ‘must have’ spell. While this ability can’t get you as far and has less overall functionality, that should be expected since misty step is a 2nd level spell. If you have allies you can position yourself around so pursuers provoke opportunity attacks then this is definitely worth it.

Since this is a simple healing spell we can compare it directly to cure wounds. At 4th level this heals 1d4+2 (average 5) versus cure wounds that we can expect to heal 1d8+2 or +3 (average 8 or 9). With the lower healing and the inability to target allies, why would I place this as a value of 1st level spell slot? Because it scales to 1d6+3 the very next level to an average of 7 and continues to scale after that.

This ones a little tough. Increasing your attack roll by 2 is statistically going to increase your damage for the attack by 10% by increasing your accuracy. For comparison spells that increase your accuracy are… true strike… Well, we will compare it anyway. This ability is made less valuable by comparison because true strike increases your attack roll by 3.4 (I’ll direct you to this article again) and also this ability requires resources. However this ability is made more valuable by; not requiring an action, by being usable after you know the result of your attack, and not needing to use it the turn before you intend to attack. Overall I’d say the positives outweigh the negatives enough for this to be worth it. I’d say that in a vacuum this is in my opinion slightly less valuable than divine smite.

For the comparison we will use silvery barbs. This ability is made less powerful than silvery barbs by; only affecting saving throws, and not also having a second effect. It is made significantly more powerful by not requiring a reaction.

It is still the full effect of the 9th level spell, just with seven less targets. It is only really useful if the DM allows it to be useful and is prepared to handle the spell, which is harder to do when only one member of the party is astral projecting.