There are two methods, you can check if it’s feasible for your requirement:
1.You can create a simple workflow associated with the list to send email to relevant users.
Then write the PowerShell to run the workflow on all items of a list as below:
# URL of the Site
$web = Get-SPWeb -Identity "http://sharepointsite"
$manager = $web.Site.WorkFlowManager
# Name of the list
$list = $web.Lists["Shared Documents"]
# Name of the Workflow
$assoc = $list.WorkflowAssociations.GetAssociationByName("WFName","en-US")
$data = $assoc.AssociationData
$items = $list.Items
foreach($item in $items)
$wf = $manager.StartWorkFlow($item,$assoc,$data,$true)
Reference: SharePoint Start Workflow on All Items of a List via PowerShell
Then use Windows Task Scheduler to run the workflow every Tuesday or Thursday.
Reference: How to: Run PowerShell Scripts from Task Scheduler
2.Add a stage at the end to put in a “Pause for Duration” action. And we can set this for 7 day (or 168 hours). For the Transition to stage, make it to back up to the first stage.
Then run the workflow first time in Tuesday or Thursday.