To gain infinite lives:

POKE 30034,201

---

Just RETurn, instead of decreasing Lives by one:

30034	LD HL,30777	Decrease *Lives by one.
30037	DEC (HL)

For infinite fuel:

POKE 30380,42

POKE 59500,58

---

Fuel is held by 30780 and 30781. This changes the following two instances where the fuel is decreased.

Altering where the decreased fuel is written back to Fuel:

30378	SBC HL,DE
30380	LD (30780),HL

To LoaD the value into HL instead of writing it to Fuel:

30380

LD HL,(30780)

And similarly, altering:

59495	LD A,30781
59498	SUB 8
59500	LD (30781),A

For a similar outcome (LoaDing into A instead of writing to 30781:

59500

LD A,(30781)