Only allow the creator of the item and the user direct manager to view the submitted item

I am facing this challenge , where we want to create a custom list, with the following logic;-

1) User submit a request asking for example for for salary increase. mentioning the amount.
2) The request need to be approved by the user direct manager
3) then the manager of the user's direct manager, need to do a second approval.

Now we need to force those permissions:-

1) once the form is submitted others users should not view this item, even for 1 minute,
2) so the item once submitted should only be viewed by the creator, without the ability to edit it
3) only the direct manager and later the manager of the direct manager can view it.

Here what i tried and what i faced:-

1) i created a custom list, define all the columns
2) create a power apps form to submit the form.
3) create a custom permission level, to allow the user to create but without edit/delete, which is mainly a copy of the contribute, without those check-boxes:-

4) then i define a power automate flow so once the item is submitted ,to send approval email to the direct manager + grant the approval manager & submitter read on the item. where i am storing the approval status inside another list that can only be edited by the service account.

this worked partially, as the item will still be visible to all users until the workflow runs. also incase the workflow fails to run the item will stay visible forever.

so i tried this second approach, benefiting from Item-Level Permissions:-

this will always force the item to be visible to the creator only, without the need to have a workflow. but we faced an issue , when we want the submitter's direct manager to view this item, to be able to approve or reject it. where even if we grant the direct manager full control on the item, the item will not be visible to the direct manager, since we define the above Item-Level permission. the only way to to fix this is to grant the direct manager's full control on the list, but in this case the direct manager will be able to view all items, not just the ones submitted by his team !

can we do this for example:-

1) create a custom permission level to only allow the user to submit without the ability to edit, delete, view?
2) then using a workflow to force the item permissions as we go.
3) in this case the item from the beginning will not be visible to anyone, then the workflow will do the permission modification. so if the workflow fails atleast the item will not be exposed to any one,

so not sure what u need to do, and if SharePoint support a way to create a custom permission level that allow the user to create without the ability to edit,delete and even view? any advice?