Managed checkout converts poorly - needs updating

Managed Checkout

• The 'show order summary' box does not disappear on galaxy devices when you pull up the keypad, this eliminates a further 10-15% of screen space and makes checking out clunky as you only have 30% of your screen to work with when filling out the fields. This box does disappear on an iphone but not on a galaxy, we're currently converting 15% less customers on galaxy devices as opposed to iphones. This is costing us a large amount of sales.
• 'Confirm Email Address' is not needed, most other big platforms have already made the shift and removed the need to re-type in your email address, it isn't needed. https://baymard.com/blog/checkout-flow-average-form-fields check out that link for why less time filling in forms = more sales
• Fields which are 'required' do not say 'required' -Fields which are 'optional' do not say 'optional' - We've watched countless customers hit the pay now button only to be flagged up with a red box telling them they've not filled in all details, this should be a simple fix.
• In some instances if a customer hits the 'paypal express' button, then hits the back button for whatever reason then decides to hit the 'paypal express' button again, it doesn't seem to work and just takes them to the managed checkout with a payment error flagged.
• If the customer wants to add a coupon code in the checkout rather than the cart, the buttons displayed say 'add discount' or 'add voucher'. We've had a fair bit of feedback from customers on the checkout page asking where to put the coupon in, for the sake of a button name change or the ability to change the buttons naming conventions ourselves i feel this should be an easy fix. ie for us, having the button say 'add coupon' rather than 'add discount' would be much less confusing.

All these changes seem pretty standard in my opinion, although some may seem a little picky, all we care about is overall conversion rates on our site and if a minor change can increase/decrease our conversion rates by even 0.1%, that's a huge deal and costs a lot in sales.

With the global average eCommerce conversion rates of about 2%, 0.1% would equal a 5% increase/decrease in revenue.