Is using Ed25519 parameters in ECDSA safe?
ECDH is the same as what Curve25519 uses mathematically. The issue is that converting Curve25519 into Weierstrauß form is a bad idea, because it introduces issues relating to the potential failure of the addition law, which are difficult to address well. Keeping the curve in Montgomery or twisted Edwards form finesses these difficulties.

ECDSA has issues related to randomness and is slow. It will be secure, but Ed25519 has many advantages; especially with batch verification.