Not specific to UA since I, and many, don't know exactly what they're after. I volunteered at AA recruiting and only the top people knew the details. We'd randomly hear very very small details but knew nothing about the big picture. We could ask the insiders and I had them say "we don't give advice....but that's good advice that you just mentioned."

I'll rewrite your info -

3600 TT
1800 TPIC in 3 different a/c
2 type ratings.

800 hrs Part 135

How much TPIC in each type? I've heard a friend very high up in the pilot hiring food chain say "we're not getting guys with TPIC time. Or it's PC-12 time." I don't know if they don't count SEL TPIC time or if they, or just he, doesn't rate it as highly. Or if it's an opinion/observation that he has that the system doesn't care about?

How flexible/mobile are you? Can you pull chocks and move to improve your resume? Compare that to the hours you're getting now. I'd look at the regionals offering quick upgrades once you get 1000 hrs of qualfiying time. They'd hire you with 950 hrs qualifying time for a rapid/direct entry upgrade. I'd ask the regional airlines directly if your TPIC and Part 135 time qualifies. If it does you're already above the TPIC trigger lines of 500/1000 hrs TPIC.

IMO the thing that stands out that you can do that would improve your resume is - go through a Part 121 school, fly a bigger jet, get a new type rating and possibly get 121 TPIC time in a couple of months (6-12?). You're already 'qualified', and might be considered 'highly qualified' (1000 hrs TPIC) if all your TPIC time is considered qualifying. Look at the 'holes' in your resume vs what others have and figure out if you can add what they have to your resume. Look 3, 6, 12 months in the future and make resumes for those time periods. Do that for your current job vs pursuing other jobs. Does doing more CItation XL, K350, of PC-6 time improve your resume? At what point is it just more ground hog time on your resume if you meet the general minimums (3000 hrs TT/500 or 1000 hrs TPIC)?