I have had your same issue with my JSN-AL00, China version, due to a drop by the water.
I have tried more or less what you have written, without success. But thanks to a hint that a user gave me, I solved my problem.
1. I totally discharged my phone (It took 3 long days) until 1% of charge or less
2. I plugged again my phone and, when it began to bootloop again, I start pressing contemporary Volume Down + Power OFF, trying to inject a spontaneous eRecovery process.
3. After several, many attempts, finally my eRecovery screen appears (it says there was a system error in upgrade. Bah?!) and I was able to boot manually and regularly it.
Be patient with step 3: you have to wait and hit the exact moment where the combination Vol Down + Power Off is definitely catched by Android.
If I remember correctly, I kept pressing - long and decisively - after the my hand felt the vibration of the start of the boot and I released my pressing a moment after blu honor logo appeared.
Hope this helps you, and let me know if it do.
Last but non least, sorry for my language, but English is not my mother tongue.
Inviato dal mio JSN-AL00a utilizzando Tapatalk