I don't know about Aucklanders but down here ours does't stink so we spread it around the radiata forests and it helps grow pretreated pinus radiata. There has been a lot of research done on this and the limiting factor is the application of nitrate (and that takes care of everything else)
You were lucky you did't have killies in there, they would have beaten the snails by a long shot. I killed over 300 once, almost instantly after treating with one seventh of the normal dose of copper sulphate.
I would doubt that it is the suckers actually. Plastic often has a plasticiser added and some may bleed out but the quantities would be so minute from 2 small suckers that I can't see it being a problem. Anabantoids and cats can survive better in bad water because of their ability to get O2 from other than their gills so I would suspect a lack of O2 which coud be caused by a bacterial bloom. In either case removing the suckers and doing water changes is about the best you can do.
The cheap ones or expensive ones are about the same. They will both end up stuffed if you abuse them by:
Cutting dirty glass
Cutting over an existing cut
not having oil on the wheel
Starting the cut right on the edge
Up to you but if I was going to stuff one I would prefer it to be the cheap one. I have both and have used both and they are all fine if used properly.
Second hand glass is fine (30 years ago all tanks were made from 2nd hand glass) You need to make sure it is clean where you are cutting and remember that glass is a liquid and the older it is the more uneven the thickness will be so the more tricky it will be to cut. If you can get it cheap enough you can afford to stuff the odd bit.
As a complete aside I know someone who has grown crypts emersed to flower and identify them. They have distinctive and attractive flowers. PM if you want more info.
Barrie has posted a good description on cutting glass. If all else fails---ask the pros
I think most killies are permitted imports as fish but are not that easy to get from the suppliers (who are normally in Europe whereas we mainly import from Asia), or from the importers point of view because there is a limited market. It is easier to sell 10000 neons than 10 pairs of killies. Many countries do allow the importation of killi eggs but not this one.
Repairing tanks can be a total pain in the butt so I wouldn't be surprised if someone charged heaps to do it. If you can get a bit of glass and do it yourself it is still a pain but a less expensive one, and it is a very useful skill to develop if you are a half handy fish keeper.
When they hatch (and are orange because of the yolk sack) they are at the best for food value. At that stage they are nuplii with no usefull parts like a mouth or anus. They feed on the yolk sack over the next 24 hours and become baby brine shrimp with all the useful parts. They are the best food value therefore as soon as they hatch. I find the best way is the old coke bottle trick.