Your bug protection and shelter seems like a safe and comfortable option. Be aware that it might be almost no bugs at all - but better safe than sorry. Usually there are mosquitoes below the treeline, and almost none above. It should not be a problem to find nice, soft and dry campingsites near clean water. Wind is maybe the most difficult thing to escape from - above the treeline. I have never seen Hex3, but from the internet catalogue it seems to give a complete wind cover.
Shelter is really not such a big problem in Jotunheimen. There are lots of mountain cabins run by the trekking association and others. Food, shelter and help from others in an emergency is not so far away. So if conditions turn so bad that your tent gives in (I cannot imagine it will), you will always have a backup. When you plan your route, just take notice where the nearest cabins are.
The "t-trails" are very well marked and follows terrain you can walk without special aids like crampons. Crampons are not necessary for walking t-trails. Not even for climbing the t-trail to Galdhoepiggen (highest mountain). There are beautiful glacier formations to be seen, and here crampons may be a good idea. Most people go with an experienced guide, who provides the necessary safety equipment. If you are unexperienced on glaciers and do not bring safety equipment (axe, harness, slings, rope, icebolts etc), I would reccommend going with a guide. Many parts of Jotunheimen is real rough, steep and rocky terrain. In the worst parts I would walk the trails.
Reindeers keep away from t-tracks, cottages and humans. Other animals, hare, fox, moose, lynx and wolwerine, is rarely seen. The calving takes place in the spring. Reindeer herds need to be undisturbed when the calves are young. If you spot them, and I hope you do, please try not to rouse them. Foot tourists on a distance is not a problem. Loose dogs are.
For a detailed map of distribution of reindeer herd origins, go to www.villrein.no It's only norwegian text, but the initial map shows that the reindeer herds of southern Norway has different origins. Some herds are genetically "wild", and others descend from domesticated reindeers, and others again are a mixture. But all herds live and die like "wild" reindeers. They are not farmed like in northern Norway, but a quota is hunted and shot every autumn. In the Jotunheimen area, reindeer descend from domesticated animals.
Gas canisters is readily available from gas stations and sport shops. Common brands are Primus, Camping Gaz, MSR and Jetboil canisters. They all fit well for the screw-mount type stoves. The gas mixture may vary, but for summer use, any gas mixture will do reasonably well. A big outlet named XXL (www.xxl.no) is close by the Oslo central station. They have low prices on most sport goods, including gas canisters. They sell canisters from Primus, a swedish brand. (www.primus.se)