I would recommend using the tool at mail-tester.com to diagnose how spam filters view your sent messages. Get a temporary email address, send them a copy of the mail that's being filtered or rejected by the recipient.

I would not recommend using +all in an SPF record, basically this says mail from this domain should be accepted from every mail server on the internet. This basically gives billions of people the authorization to send mail from your domain. The mx part of the spf record does say that mail sent from any server that receives your domain's mail should be considered valid. ~all or -all are probably better options. -all means the list is exhaustive and mail sent from any host outside the list is a forgery (HardFail) , ~all is a less stringent Soft Fail.

As far as PTR records, most mail servers are going to check that the PTR hostname/domain references back to the ip you're sending from. If it matches the helo your server sends in the smtp connection that's also good. Again, mail-tester.com will show you a quick view of what checks it does and which are detected as problematic for your setup. This won't show Yahoo or Gmail's internal filters, but most filters will look for the same information generally.