Gauge Adjustment Help!

I am making a hat, and where the pattern calls for 158 stitches, I only used [B]110[/B] stitches for C.O and went up a needle size (sizes [B]3 and 4[/B]) and am CLUELESS on how to go about[U][I] adjusting the decreases[/I][/U]. Any ideas? I would be so grateful! Its such lightweight yarn, and pure black, so I can’t take it out! THANK YOU!!!

Here is the pattern:
Hat is knitted in the round on circular needle.
Cast on 158-170 sts on circular needle 2.5 mm/US 1or2 with Delight. K1 round. Continue in rib K1/P1. When rib measures 4-5 cm / 1½"-2" K1 round AT THE SAME TIME dec 30-34 sts evenly on round = 128-136 sts. Change to circular needle 3 mm/US 2or3. Continue in the round in stockinette st. REMEMBER THE GAUGE!
Continue like this until piece measures approx 17-19 cm / 6 3/4"-7½". Now place 8 markers in piece with 16-17 sts between each marker. Continue in stockinette st AT THE SAME TIME dec 1 st before all markers (= 8 dec) – SEE DECREASING TIP!
Repeat dec on every other round a total of 14 times = 16-24 sts.
On next round knit tog all sts 2 by 2 = 8-12 sts.
Cut the thread and pull through the remaining sts.
Tighten and sew away ends.
Hat measures approx 26-28 cm / 10 1/4"-11".

You can decrease proportionately from 110 to 90sts for the first decrease, Check that this number of sts will give you the size hat that you want by calculating the measurement in inches from your gauge. When you get to the decreases for the crown, decrease once every 10sts by knitting 8sts and then knitting 2tog around the hat.