Ice is perfectly fine. I have never had a problem with ice and I often buy ice at local street vendors where locals eat. I truely think sometimes people get hold of very very very old travel guides and take advice from 20 years ago.
Malaria can be a problem on Lombok. You should talk to your GP about malarial medication. The risk is much greater if you are there in the wet season (Nov to Mar) and also it is worse on the Gilis.
Malarone tends to be the drug of choice as you only need to take it 1 week after leaving the malaria area but it is quite expensive (about $80 for a . Personally I would view it a bit like travel insurance. The other option is Doxycycline - but while it is considerably cheaper, you MUST take it for 4 weeks after leaving the malaria area (or don't bother taking), and it can cause some nasty side effects, including beintg prone to sunburn - not what you want when spending your days in the sun!
It is important to do what ever is possible to prevent malaria - so use an insect repellent with DEET, sleep under a net. Have clothes that allow you to cover up if mosquitos are active - i.e. long cotton pants and loose long sleeve cotton shirt. Malaria mosquitos bite early morning and evening/night.
Like Bali, Lombok also has dengue. There is no meds for dengue. Dengue mosquitos bite during the day.
To me, staying in a tourist area outside of the wet season (and not on the Gilis) the risk is similar to getting Ross River Virus in parts of Australia.
Do talk to your GP about your options. Personally, after living in Lombok (so not able to take meds), and visiting every year for maybe 14 years now, I have stopped taking anti-malarials on my holidays. I am pretty careful about not being bitten though, and if I am somewhere where there seem to be a lot of mosquitos, I move on.
About the only time I get sick is getting the flu off someone on the plane going back to Australia!