As for the one error; it says how to fix it. Contact your ISP to add the reverse DNS record for your IP address.
The 'TLD Parent Check' I don't think you can fix.
'Different subnets' - this refers to the preferred setup of two or more geographical separated nameservers. This is recommended for in the case that one nameserver may be unavailable due to a failure; the other nameserver still makes sure your domain names are alive in the DNS. If you only use one physical server, and it gets down for a like half a day, your domains will be gone for a whole day. Also e-mails being sent towards your server will error back to the sender. If you have the second nameserver, the e-mail would try to resend for a long time untill your server is back up. So anyway its really a good idea to have a second nameserver on for example a little VPS.
The other warning 'Different autonomous systems' is caused by the previouse one.