Hello,
- It is definitely possible to Trigger the Lightbox using a Button, simply use the data-lightbox="inline" function. An example is already provided in the lightbox.html Template. Code:
<a href="#myModal1" data-lightbox="inline" class="btn btn-secondary btn-lg">Trigger Modal</a>
Simply change the href="#myModal1" Value according to your Modal's ID.
- If you use the following code as an example for the Modal:
<div class="modal1 mfp-hide" id="myModal1">
	<div class="block divcenter" style="background-color: #FFF; max-width: 500px;">
		<div class="feature-box fbox-center fbox-effect nobottomborder nobottommargin" style="padding: 40px;">
			<div class="fbox-icon">
				<a href="#"><i class="icon-screen i-alt"></i></a>
			</div>
			<h3>Responsive Layout<span class="subtitle">Adapts well on Devices</span></h3>
		</div>
		<div class="section center nomargin" style="padding: 30px;">
			<a href="#" class="button" onClick="$.magnificPopup.close();return false;">Don't Show me Again</a>
		</div>
	</div>
</div>
Simply change the max-width: 500px; Value and this will make your Modal Wider.
This will definitely work fine. Hope this Helps!
Let us know if we can help you with anything else or if you find any further issues.