Job switch

Hi everyone, I am working in a service based giant of India for the past 2.4 years on Ruby on Rails. Ruby is a dying language & I need to switch as my salary is lower than what peons probably earns so need some guidance.

1. I am wanting to switch to Frontend completely and then some backend in a new company in MERN stack, what salary can I expect for my YoE ?
2. With all layoffs going, how can i make myself somewhat immune to these situations so that I don't have to search for a new job every few months ?
3. Starting frontend and then will be doing backend as well (becoming Full stack) is my choice of MERN stack correct ?

Thanks in advance to all...