Questions about Picker in Xamarin.forms

I am creating a mobile application in which the user can register x ingredients and later can register products choosing which of the registered ingredients that product uses. In this perspective:

Doubt 1 : I am trying to popular a Picker with reference to the data table of the ingredients filled by the user, but I am stuck at the time of typing the connection part and adaptation of the table ... How can I do that?

Doubt 2 : The Picker allows the user to select only one option, it seems ... Is there a way to make multiple selections? Or maybe some substitute tool (in that case, you would need to know how popular that tool is with the table data).

Picker class: link

public class PickerMVVMViewModel
{
    public List<listIng> listarIng { get; set; }

    public PickerMVVMViewModel()
    {
        listarIng = GetIngs().OrderBy(t => t.Value).ToList();
    }

    public List<listIng> GetIngs()
    {
        var ing = new List<listIng>()
        {   // essa parte supostamente receberia os dados da tabela, mas fiz esses itens para checar o funcionamento.
            new listIng(){Key = 1, Value= "Pão"},
            new listIng(){Key = 2, Value= "Carne"},
            new listIng(){Key = 3, Value= "Ovo"},
            new listIng(){Key = 4, Value= "Presunto"},
            new listIng(){Key = 5, Value= "Queijo"},
            new listIng(){Key = 6, Value= "Bacon"}
        };
        return ing;
    }
}


public class listIng
{
    public int Key { get; set; }
    public string Value { get; set; }
}  

XAML that implements Picker: link

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="OrganizeSe.cadProduto">

    <StackLayout Margin="10,10,10,0">
        <Entry  Placeholder="Insira o nome do produto"                
                FontSize="20"/>

        <Label Text="Selecione os ingredientes:"
               FontSize="20"
               TranslationX="5"
               TranslationY="15"/>

        <Picker Title="--Selecione--"
                ItemsSource="{Binding listarIng}"
                ItemDisplayBinding="{Binding Value}"/>
    </StackLayout>
</ContentPage> 

Content found at table: link

    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class NewIngPage : ContentPage
    {
        public NewIngPage ()
        {
            InitializeComponent ();
        }

        private void Button_Clicked(object sender, EventArgs e)
        {
            Ingredientes ing = new Ingredientes()
            {
                Nome = nameEntry.Text,
                Preco = precoEntry.Text,
                Qnt = qntEntry.Text
            };

            using (SQLite.SQLiteConnection conn = new SQLite.SQLiteConnection(App.DB_PATH))
            {
                conn.CreateTable<Ingredientes>();
                var numberOfRows = conn.Insert(ing);

                if (numberOfRows>0)                
                    DisplayAlert("Salvo!", "O ingrediente foi salvo com sucesso.", "Ok");
                else
                    DisplayAlert("Falha!", "O ingrediente NÃO foi salvo.", "Ok");
            }                        
        }
    }