not too hard. you might wanna go inside the to pick up health. just pick up 2 weapon upgrades for the spread. more will do gain a new level with a new color(more damage) but reset your spread level. Circle around and dodge it. Nukes are probably the most risky, but sure if you think that helps go ahead. Useless in survival since enemies respawn directly if you use one.
tip for skull catch: you all know spider eye kills all enemies on screen so you easily can get enough skulls. but then theres the problem of beating the level to keep the medal. Luckily skulls replenishes energy, so don't stop collecting skulls after it says you got the medal and fill the energy bar. This energy, like in Paris, should be used for an attack to destroy the Eiffel Tower which always survive long enough to get you killed and having to restart otherwise.
tip: all characters have individual inventories. Plan who is going to carry which item so you always can get good consumables to use in battle and not risk one having all potions locked when she/he dies.
3 lizards: all 3 attacked Sharla, but she survived. I healed her with Mardek and then all 3 attacked Mardek. Coincidence or an actually smart AI that tries to take out healer first?