Yeah - until we get IPN working with the PayPal Sandbox, you will not have a donation record to observe (they are stored in database transients until PayPal shows a Completed payment status)
Thanks for sending the log - that helped! So looking at your log confirms that the transaction is starting but it looks like the PayPal developer sandbox is not initiating an IPN to your site (you should see an IPN processing start message in that log)
I was able to browse to your IPN URL directly (you might see a null IPN in your log now from that - you can ignore that)
I was also able to use the IPN testing facility at PayPal to successfully send a test IPN to that URL (its a great resource - https://developer.paypal.com/webapps/developer/applications/ipn_simulator - use Express Checkout as the transaction type) - you can ignore that in your log as well.
That leads me to believe there is something amiss with your PayPal developer sandbox account setup.
Make sure your PayPal sandbox account (where you are sending the donations) is configured as follows:
Account Type: Business
Payment Review: Off
Negative Testing: Off
You should not need to set an IPN in your account, but you can try that as well.
Let me know if any of these settings were incorrect and if changing them fixed the problem. Once you get an IPN to complete, you'll be able to see donation records in the database.