1. For the purposes of strict matched betting, you're better off not picking outcomes you think will win or lose. You just want close matches.
2. 2.8/2.92 is not a close match, and you're losing 11% of your back stake each time. On MSE the rule of thumb is 5% loss for qualifiers and stake return bets and, while this is not something that is necessarily strictly upheld, its certainly quite easily achievable with a little patience.
3. You can underlay your first bet or two to reduce your liabilities if your bet wins at the bookies (meaning you have to complete the WR). For instance, if you take your 2.7/2.92 match and, instead of laying 188.15 you lay 177.08, your liability drops to 340.00. This means that, if you win at the bookies, your bonus is still 100% intact. On the other hand, if your bet loses your returns are only 168.23 - a 68.23 profit rather than 78.75, but you've bust out.