Hi Pingster,
No worries, love to share my experience with reefers who are similar in my shoes...
1). Firstly, need to know if your tank depth is same as mine, 6inches or bigger? If bigger, you will have lesser restriction than me. Congrats!!! LOL.
2). Yes, the lighting is one of the contributing factor for the algae boom. These brown ones are more like diatoms, if I m not wrong. This is due to high Nitrate/Phospate and with long lighting on. So to solve this problem, you'll need to control your water parameters regularly and maybe shorten your lighting hours. Do use, anti-nitrates/phosphates media in your filter compartment as a start. Next is to do weekly WC. Btw, I used to use a toothbrush to clean the backdrop weekly!!! Now i don't and it's covered with unsightly green algae... looking for sea urchins to do the job for me.
3). Skimmer helps to reduce micro substrates like leftover fish food decomposing, etc. If you are keeping only small marine fish, then skimmer is not a must but compensate with weekly water change. But if you have intention to go into corals, it is only wise to invest in one.
4). Dun believe too much in what shops say. I were even told to top up with tap water!!!! What I practice is to buy NSW from our local LFS and do 30-40% WC at least once a week. Distill water (NTUC brand, 3 x 1.5L bottles for $1.35) is always at stand by to top up the water lost due to evaporation. For WC, NSW is enough for us as our tank volume is not that much compared to others. I will buy about 20L ($4 only) weekly.
5). Yes, the water temperature and salinity is very crucial to shrimps and invertebrates. I too had experienced such death to my shrimps even with acclimatisation. You'll have to be very patient to acclimate them. Usually, I would buy more than what I want just in case, as 50% may just die off after a few minutes. Check out the forum on how you can do proper acclimatisation.
6). Central area, can go to Reborn at Lavender Street (its where I buy my NSW) or Henry at Hong Leong Gardens (SRC sponsor), there are also our forums sponsors where you can get your stuff.
Hope this helps. You'll learn as you go along with this hobby, but my experience tells me that you must read and do your own research before getting any LS bcos our tank has very high limitation and some LS are very sensitive to these limitations. Our wall mounted tank will make this hobby double challenging!!!!
Feel free to contact me if you need any other advise, will help if I know although my knowledge also Pte Ltd.
Happy reefing.