Need to stop a stylesheet from loading

Hi – I am a total noob and this is my first time migrating a static site onto wordpress.

One of the main troubles I’m having regards loading stylesheets only on specific pages or while using specific templates.

I have a page that continues to load a stylesheet that I don’t want to use on it. I’m not an expert at CSS or PHP, so I can’t see why it’s loading even though I’ve specified a different stylesheet in header.php.

Here’s the way the page SHOULD look:
https://www.phoenixrisingtheater.org/contact.html

and here’s what’s happening in wordpress:
https://www.phoenixrisingtheater/dynamic/contact-2

I don’t want “singlecol.css” to load on this page, I want “twocol.css” and the main style.css only.

And I’m sorry it’s such a mess, but here’s my code from header.php:

<link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/default.css" type="text/css">
<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css">
<link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/footer.css" type="text/css">
<link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/nivo-slider.css" type="text/css">  

<?php if (is_single) { ?>
     <link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/singlecol.css" type="text/css" media="screen" />
<?php } else { ?>
     <link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<?php } ?>

<?php if (is_page('about') ) { ?>
     <link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/about.css" type="text/css" media="screen" />
	<?php } ?>

<?php if (is_page_template('twocol.php') ) { ?>
     <link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/twocol.css" type="text/css" media="screen" />
<?php }	else { ?>
	     <link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />

	<?php } ?>

<?php if (is_page('current-season') ) { ?>
     <link rel="stylesheet" href="<?php bloginfo('template_url'); ?>/css/singlecol.css" type="text/css" media="screen" />
<?php } else { ?>
     <link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<?php } ?>

Any tips for cleaning this up would be appreciated as well. ??

Thank you in advance!