running total with IDs and nonsequential dates

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test (later on when you use the query on your dataset, you will have to change the source appropriately. If you have columns other than these, then delete Changed type step and do a Changed type for complete table from UI again)

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("dc3LDYAwDAPQXXKulNqhpcxSdf81AKmfgOCY58iuVUCTIIhKKiNxHZQWZkDFcHPema93U/tm/vAxvJenvN+rqz1535SzvzwDFLfQTg==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, Date = _t, Points = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"Date", type date}, {"Points", Int64.Type}}),
    ListOfIDs = List.Buffer(#"Changed Type"[ID]),
    ListOfDates = List.Buffer(#"Changed Type"[Date]),
    ListOfPoints = List.Buffer(#"Changed Type"[Points]),
    //Function Start
    fxGetCumTotal=(ListOfIDs, ListOfPoints)=>
        let
            FunctionResult = List.Generate(()=>[x=ListOfPoints{0},i=0], each [i]<List.Count(ListOfPoints), each [i=[i]+1, x=(if ListOfIDs{i}=ListOfIDs{[i]} then [x] else 0) + ListOfPoints{i}], each [x])
        in
            FunctionResult,
    //Function End
    Result = Table.FromColumns(Table.ToColumns(#"Changed Type")&{fxGetCumTotal(ListOfIDs, ListOfPoints)},Table.ColumnNames(#"Changed Type")&{"Running Total"})
in
    Result