Black Flag questions... re-obtain previously unlocked gear, re-obtain resource pack, and some achievements.

Hi all... couple real quick questions... With the news of the Black Flag remake being official-official now, I thought I'd go back and replay the original (and finish up my missing 19 achievements) with all Ultra graphics and ultra-wide mod and all that goodness. Made it to sequence 3, mission 5 last night (gotta go see Capt Kidd about robbing a plantation)...

1. Way back in the day, I bought the "resource pack" to speed up some ship upgrades. Was that a 1-time thing? Does it not work on subsequent New Game playthroughs? I've upgraded my ship's armor and cannons and added a ram, changed out my sails, etc... but it doesn't seem like I have what I should. I can live without it, but just wondering nonetheless.

2. I can see the 5-5-3 super pistols at the shops (forget the name now) that you get for beating all the contracts or naval missions (also forget which)... Says they cost 0 reales, but I can't use/equip them. Do they not carry forward to subsequent playthroughs, and I have to unlock them again?

3. Lots of my remaining achievements are related to the Adawale DLC... but I don't see anywhere to launch that. Does it unlock at some point, or am I just missing it on the main menu somewhere?

4. Lots of my other remaining achievements are related to the multiplayer... Can those be solo'd with bots? Or will I need to play against real people? If the latter, is there a "boosting" group or discord or subreddit or anything to make it more tolerable (if not solo-able)?

Thanks a bunch for any answers yall can give. So far, having a blast re-playing, forgot how much shit there is to collect in each town/island. >_<