Form Fields and Submit button not centered

I have a very simple opt-in form (first name and email) and it looks okay on the desktop and skewed right on the mobile iPhone: http://www.buddhainspired.com
What do I need to do to get a clean centered alignment?

I also created a brand new sign up form and besides a few color changes, left most default settings. This looks awful on deskop – the border is way too big, all the fields left justified. And it is fine on mobile! What am I missing in using this plug-in? http://www.buddhainspired.com/sign-up/

I have been fiddling with these sign up boxes for way too long and getting ready to ditch Magic Action Box – please help. If I ultimately need to upgrade to Pro to solve these issues, please advise how easy it will be to use.

Many thanks in advance.

https://ww.wp.xz.cn/plugins/magic-action-box/