The easiest question to answer here is that yes, as a bronze/silver account your AA bar will be fixed. It only moves at level 10, and level 90(in other words, before you can get AAs its at 0 and once you can no longer level its at 100 - itll be 50 the entire time inbetween).
Velious is indeed skippable. Just picking up AoD will get you mercs, a tradeskill apprentice, the dungeon maker, beastlords... and i think 20 extra AAs. Its possible that Dyadem was confused on the dungeon maker part because you can play IN someone elses dungeon without the expack, but you can only design your own if you picked it up.
What you give up in the DoV pack is a lot of the best high level(85+) adventuring content, the only current tradeskill heritage quest... and maybe flight and the new raised level cap? I dont think they let you go to 92 without DoV(you definately wont get the new standard trade recipes, as those only come from quests in a DoV zone), and im not sure if you can get a flying mount without the pack(you definately can not do the quest for one, im not so sure if you bought one off the marketplace without the expack if itd let you fly... but no one can fly before they get either adventure or crafting to level 85, so this is a question for later).
One thing you could consider is waiting til the next time they go on sale(or a double+ SC weekend) and getting the pack for a discount. A $15 walmart card applied during a triple SC weekend(admittedly, these are much more rare then double credit weekends) would get you enough SC to tag yourself for both expansions. You know, if you wanna wait that long. Otherwise, just play what you wanna play, its all good.