A few more titles that you will hate, but actually describe your role. You are in no sense just a senior developer.
You are an
- Architect
- Solution Architect
- Project Manager and Team Leader
- Service Manager
Which one fits best, you have to decide. But i would put this up on my resume if i had your responsibilities.
I guess the best way for that, is to crosscheck with the maiantained list on the megathread of this community.