Hi PK - you've learned a huge amount this past season, so good work; some answers below...
Re: SS, the guy you suggest is OK vs. RHP isn't so hot. He'll play adequate defense, which is crucial, but his bat is not so good, even vRHP. For a season or 2 of cheap service, he can do. Versus lefties, fear not: SSs are overwhelmingly right handed, and that typically makes them better vLHP. You will either find a waiver wire castoff, a Rule 5 draftee, or a cheap f.a. (see below) that bats well against lefties but is atrocious vs. righties. There's your SS platoon, and it will cost you nothing.
Re: draft: you've got the #1 pick, and that's probably more important than anything else you asked about. Take the best player available, whether it's a starting pitcher or a CF or a SS. Best player, whether perennial MVP-candidate or Cy Young-contender. There's no point targeting specific positions in the draft: if you get the best player available, you'll be able to trade for what you need later.
You correctly appreciate that it's a big deal having #1 priority on the WW at this stage. There will be castoffs for a period of weeks before the season even starts, and with a ML-roster as (sorry!) bad as yours, you've got room to take them as they come. Only a few on the WW are legit MLers, but they turn up, and my first playoff team had quite a few guys claimed off waivers.
Rule 5: trust the ratings, not the level of ball they play. If a GM just forgot to promote them or was negligent, players with good ratings and growth potential can be mired at the low levels. Some prospects get left at rookie level for 2 or 3 seasons, which is just silly indeed - it denies prospects half a season of playing time and development. I digress... Go with ratings. If they are good enough to play the bigs, draft them.
Free agents reduce their demands after a few days on the f.a. market in which they don't receive bids. Falling demands includes both annual salary and # of years covered. Once spring training starts, expect remaining free agents to get much cheaper. Those leftovers are often pretty good, too, but (as always) you need to be selective. You're unlikely to find all-stars, but there are guys who can excel as part-time or situational contributors, and there are many vets whose initial demands spooked off other owners (5 years at $6M for a 34 y.o. SP???), but when their demands fall they are absolute bargains (2 years at $2.5M? Word booty-).
Hope this helps, and good luck with your team craft. Judging by your last amateur draft, you learned a lot in predicting ML-quality talent.