2.1.0.2 with PayPal Standard - email order notifications

Hello,
I've created a site for someone using OpenCart 2.1.0.2 and it works great, it takes orders and accepts payments(via pp standard), all good!
However, although it works great there are a few things not quite right which are important. I'm after some knowledge/advice as to why I'm encountering these problems please.....and how I might fix them?
Firstly, the site is hosted with BlueHost, the domain is registered with 1and1 and the emails run via Google's G Suite. It has to be this way because that is how/where they have their domain registered which they don't wish to transfer.

1) There is a problem with email order notifications not being delivered. Some are and some aren't. There are no errors in either the OC log nor the PP IPN history, I even submitted a ticket with PP Merchant Technical Support who have responded saying everything regarding IPN is perfectly functioning. I do receive all contact form submissions and customer sign-up email notifications. Although the site is for someone else, I have my email added to the 'additional email' field for the moment to manage this missing email issue and I don't receive any order notification emails....?

2) When a failed email attempt to contact happens i.e. a rejected contact form submission and another case where someone had a auto-reply/out-of-office email set which responded to their order notification, these failed attempts are sent to my BlueHost hosting email account and not the actual sites email address....? I contacted BlueHost and they suggested my mail parameter should be '-f '(space between lowercase f and address) where I currently have it as '-F'(no space between uppercase F and address), the latter being what works for everything else and what I've seen/read many advise.....?

3) Lastly, every now and then a completed and normally processed executed order doesn't appear in the 'recent activity' list on my dashboard. Is this a underlying issue which can and should be corrected....?

Any advice you have would be greatly appreciated. I wondered if these issue are all related...?

Thanks,