How sensitive to change are elliptic curve formulae In layman's terms?
An elliptic curve equation is very sensitive to any change of its parameters.

That small change result in a complete different curve.
Its security could be good or bad, but you have to check it explicitly and cannot make predictions beforehand.

Specifically, your resulting curve will have a composite order whose largest factor is $833860344743147476600479140946265460420135480673538361531$ which implies your curve's security won't exceed $2^{94.5}$.
I said "won't exceed" because I haven't checked all the other security properties of the curve (twist security, transfers, etc), which could result in a security downgrade.