Hi Eabha,
Fellow T1 here, welcome to the Premier League of diabetes!
You haven't wasted any time getting to grips with it and that's very impressive (head in the sand is soooo much easier).
All your meds, including test strips, should be free on prescription. If your doctor tries to restrict your test strips, ask him what he would do if faced with the risk of hypoglycemia.
Yes, insulin is an anabolic (fat building) hormone. You are slim, like most T1's, often because of this chronic lack of insulin, but the pounds will creep on if you abuse the stuff.
Replacing sweet with fat is a very smart move. You'll need much less insulin, you'll stay slim, and your lipids (cholesterol levels) will be the envy of your friends.
Keep it up, you're off to a great start.
fergus