The PTR record is, in most (default) cases, only important for the MX server's hostname (i.e. the host which is connecting to the destination SMTP server), not for the sender address/domain (i.e.
From: field in the mail headers). Otherwise, multiple MXes for the same domain wouldn't be possible. Most MTAs' checks for domain and PTR records matching only take place for the hostname presented in the
EHLO command of the sending e-mail server, which can naturally be totally different than the domain in the sender address. It's just important that the sending SMTP service "authenticates" itself to the remote SMTP service via stringent DNS/PTR records.
To do things clean, you may configure a subdomain of your domain (like exchange.yourdomain.com) with a DNS A record pointing to the IP address of the Exchange server. Then you configure the Exchange server's IP address's PTR record to exchange.yourdomain.com. Also, configure the Exchange server to present exchange.yourdomain.com when
EHLOing the destination server (you may find hints on how to do so here). This should be sufficient with most destination hosts.
As far as I'm concerned, you shouldn't need to touch the GSuite configuration since everything is working fine with it.