Questions about Picker in Xamarin.Forms

Question

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

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

Doubt 2: Picker allows the user to select only one option, it seems... Is there any way to select multiple options? Or maybe some replacement tool (in this case, you need to know how popular this tool with table data).

Picker class: https://pastebin.com/2iFZWbhs

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 implementing the Picker: https://pastebin.com/pPj64c7t

<?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 in table: https://pastebin.com/v66JSJt

    [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");
            }                        
        }
    }