It would be hard to achieve what you ask with knockout templates, this is why I suggested using a standard HTML form and some simple JavaScript.

The JSON API call, using jQuery would be:

$.ajax({
	dataType: 'json',
	data: {
		'__wallets_apiversion' : 3
		'__wallets_action' : 'do_withdraw',
		'__wallets_withdraw_address' : address,
		'__wallets_symbol' : symbol,
		'__wallets_withdraw_amount' : amount,
		'__wallets_withdraw_comment' : comment,
		'__wallets_withdraw_extra' : extra,
		'_wpnonce' : wp.wallets.viewModels.wallets.nonces()['do_withdraw']
	},
	success: function( response ) {

		$( form ).trigger( 'wallets_do_withdraw', [
			response,
			symbol,
			amount,
			address,
			comment,
			extra
		] );

	error: function() {
		alert( 'Withdrawal not submitted' );
	}
});

Just make sure to attach this to whatever button your form has, and pass the variables in from the form.

Hope this is a bit more clear. The rest is just standard html/javascript.

with regards